Non-invasive diagnostic assessment tools for the detection of liver fibrosis in patients with suspected alcohol-related liver disease: A systematic review and economic evaluation

Aetiology

Alcohol-related liver disease is caused by the consumption of substantial quantities of alcohol. In the UK, alcoholic drinks are measured in units corresponding to approximately 10 ml (8 g) of ethanol. 6 Previously, the minimum alcohol intake associated with significant liver damage was thought to be around 20 units a day for 5 years and the likelihood of light to moderate drinkers developing cirrhosis was considered very remote. 7 More recently, it has been suggested that all people whose daily alcohol consumption exceeds 80 g (10 units) will eventually develop steatosis; 10–35% will develop alcoholic hepatitis, and approximately 10% will develop cirrhosis. 8 However, because steatosis is usually, and hepatitis and cirrhosis sometimes, asymptomatic, many will be unaware that they have ALD; indeed, 30–40% of cases of cirrhosis are not discovered until autopsy. 1

Pathology

As noted above, the term ALD covers a spectrum of illness. The majority of individuals who abuse alcohol will develop steatosis,9 a condition characterised by the accumulation of excess fat within the liver cells. 10 Steatosis is usually asymptomatic, but may manifest as changes in liver function test results; it is reversible if alcohol consumption is stopped or significantly reduced. 1 However, approximately 20% of people with alcoholic steatosis who continue long-term alcohol consumption are likely to develop fibrosis and cirrhosis. 2

In a minority (perhaps < 20%) of alcohol misusers, alcoholic steatosis evolves with the development of inflammation and cell death within the liver. This phase of injury is known as alcoholic hepatitis. 10 The majority of patients who develop alcoholic hepatitis are asymptomatic, but others suffer non-specific symptoms such as nausea, vomiting, and abdominal pain, whereas others present with acute alcoholic hepatitis (AAH), which is characterised by abdominal pain/discomfort, fever, a high white blood cell count, abnormalities of blood clotting, jaundice, and other features of liver failure. 1 Patients with mild alcoholic hepatitis will recover well, with reversal of the liver damage, if they stop drinking. Progression to cirrhosis is more likely in women than in men, and in individuals of both sexes who have severe alcoholic hepatitis on presentation, irrespective of their future drinking behaviour.

Repeated episodes of alcoholic hepatitis may result in the development of scar tissue known as fibrosis; this can be localised or diffuse, and can eventually lead to distortion of the architecture of the liver by broad fibrous bands and the development of regenerative nodules, which are the hallmark of cirrhosis. Patients with cirrhosis may be asymptomatic, and their liver function tests may show few if any abnormalities; such patients are described as having compensated disease. 10,11 In a recent Danish study, 24% of patients diagnosed with alcoholic cirrhosis had no complications. 12 Patients with cirrhosis may, however, develop a number of complications as a result of hepatocellular failure and the development of portal hypertension (PHt). Hepatocellular failure results in loss of the liver’s ability to deal with waste products (e.g. bilirubin from red blood cells, toxins produced in the bowel such as ammonia, and drugs) and impairment of its synthetic function leading to low levels of body proteins such as albumin and the factors responsible for blood clotting. PHt develops when the passage of blood from the intestine and the spleen, which is usually cleansed and detoxified in the liver, is impeded because of the presence of fibrosis. As a result, collateral vessels develop to bypass the liver to ensure that the blood gets back to the heart. These collateral vessels may develop in the stomach and oesophagus and may rupture when the pressure gradient within the portal system [the hepatic venous pressure gradient (HVPG)] exceeds 12 mmHg. 13 Hepatocellular failure and PHt result in the development of several problems, including jaundice, ascites, variceal bleeding, and hepatic encephalopathy (HE). 4 Patients with these complications are described as having decompensated cirrhosis. Each year, approximately 5–7% of patients with compensated cirrhosis will develop decompensated disease. 4 Approximately 20% of patients with cirrhosis will go on to develop HCC; this is more common in men than in women and in those who have stopped drinking (Dr Marsha Morgan, Royal Free Hospital, London, 2010, personal communication).

Alcoholic hepatitis and cirrhosis may co-exist within the same patient: thus, it has been reported that 50–60% of patients diagnosed with AAH already have cirrhosis at the time of diagnosis. 14

Measurement of disease

Traditionally, liver biopsy has been used to obtain histological samples from patients suspected of having ALD. These biopsy samples are used to confirm the diagnosis of ALD, exclude other or additional liver pathologies, and provide accurate staging of the degree of liver injury in order to enable the prediction of prognosis and inform treatment decisions.

Various semi-quantitative scoring systems have been developed to measure and categorise disease progression in biopsy samples. The most widely used system, the METAVIR system, has a grading system that scores the degree of inflammation from 0 to 4 (where 0 is no activity and 4 is severe activity) and a staging system that categorises the degree of architectural change and consequent severity of the underlying liver disease15 from none (F0) to mild (F1), moderate (F2), severe (F3), and cirrhosis (F4). It should be noted that METAVIR, and other similar systems, have been described as being, at best, ordered categorical data;16 they do not represent an arithmetic progression, and consequently, for example, a METAVIR score of F4 does not involve twice as much scarring as a score of F2. For further details of the various scoring systems referred to in this review, see Appendix 1.

In clinical practice, various boundaries are said to be significant. These are the boundaries between no-to-mild fibrosis (F0–F1) and significant fibrosis (F ≥ 2),17 and between mild-to-moderate fibrosis (F1–F2) and severe fibrosis or cirrhosis (F3–F4). 18 However, the former seems primarily relevant in viral hepatitis, where F2 fibrosis forms the threshold for the initiation of interferon therapy;19 it arguably has less relevance in ALD, where the boundary between F0–F3 and F4 appears more important as it forms the threshold for the initiation of regular screening for varices and HCC.

Prognosis

Prognosis in patients with ALD is strongly linked to the degree of disease progression. In an early UK study, Saunders et al. 20 found that 5-year survival in adults identified between 1959 and 1976 as having alcoholic cirrhosis was only 36%; most already had decompensated cirrhosis at diagnosis. More recently, Jepsen et al. 12 found that the median survival in Danish patients diagnosed between 1993 and 2005 with alcoholic cirrhosis without complications was 48 months. The 1-year mortality ranged from 17% in those who presented with no complications to 64% in those who presented with HE; the equivalent 5-year mortality figures were 58% and 85%, respectively. More generally, median survival times for patients diagnosed with compensated and decompensated cirrhosis have been estimated at over 12 years and around 2 years, respectively; most patients originally diagnosed with compensated cirrhosis die only after the development of decompensation. 4

In patients with cirrhosis, the presence of superimposed alcoholic hepatitis and the development of hepatocellular carcinoma significantly reduced survival. Verrill et al. 21 found that 30-day mortality in patients with cirrhosis and alcoholic hepatitis was 27%, while Orrego et al. 22 found that the 1-year and 5-year mortality were significantly higher than in those of patients who had alcoholic cirrhosis alone, and Chedid et al. 23 found that 65% of patients with concurrent alcoholic hepatitis and cirrhosis died within 4 years of diagnosis, mostly within the first year. Alcoholic cirrhosis substantially increases the risk of hepatocellular carcinoma,1 which, again, has a poor prognosis: 1-year survival after diagnosis of HCC is about 20%, 5-year survival about 5%,24 and approximately 15% of patients who develop alcohol-related cirrhosis will die of HCC. 9

However, the outcome for patients with alcohol-related cirrhosis is substantially determined not only by the degree of decompensation at presentation but also by subsequent drinking behaviour. In 2004, Tome and Lucey25 suggested that, in people with clinically compensated cirrhosis, the 5-year survival was about 90% in those who abstained compared with about 70% in those who did not, whereas in 2003 Mann et al. 1 suggested that, in patients with late-stage, decompensated cirrhosis, the 5-year survival was 60% in those who abstained, but only 35% in those who did not. In a recent study, Verrill et al. 21 found that patients who reported being abstinent from alcohol 30 days after receiving a diagnosis of alcoholic cirrhosis had a 7-year survival of 72% compared with 44% in those who continued to drink. A considerably older study by Saunders et al. 20 found that 10-year survival in patients who abstained completely from alcohol was nearly 60% in those who presented with compensated cirrhosis and around 50% in those who presented with decompensated cirrhosis, compared with around 30% and < 10%, respectively, in those who continued drinking. It is currently estimated that a middle-aged man who presents with compensated cirrhosis and subsequently abstains from alcohol has a 60–80% chance of being alive in 10 years, whereas a similar individual who presents with, for example, variceal bleeding, and who survives the initial presentation but who continues to drink, is unlikely to survive more than a year or two (Dr Marsha Morgan, Royal Free Hospital, London, 2010, personal communication).

A small study by Day,26 of 96 patients with biopsy-proven ALD and a weekly alcohol intake of 135 ± 8 units, suggests that a reduction in alcohol intake may also be beneficial. No difference was found between abstainers and mild/moderate drinkers in either mortality (total or liver-related) or the development of new liver complications; however, continued heavy drinking (> 50 units/week for men and > 35 units/week for women) was predictive of both total and liver-related mortality.

Alcohol consumption also has a marked impact on prognosis in patients with milder forms of ALD. With abstinence, hepatic steatosis appears to be completely reversed within several weeks and AAH usually improves. 25 Patients with hepatic steatosis who stop drinking have a near-normal lifespan; future drinking behaviour is the most important determinant of outcome in this patient group. Their prognosis has improved over time as the treatment of their complications has become more successful. Moreover, as Chedid et al. have shown,23 these patients tend to die as a result of their alcoholism rather than their liver disease. Thus, although the 2-year survival in patients with alcoholic steatosis is only 70%, those who die do so as a result of other alcohol-related events such as accidents, injuries, suicide, and homicide, not their liver disease. However, although some patients with alcoholic hepatitis who abstain from alcohol make a complete recovery, others develop cirrhosis despite abstinence. 10

Although only a minority of patients with ALD abstain from alcohol following diagnosis, the proportion may be increasing; although only 19% of patients in a UK study who were diagnosed with alcoholic cirrhosis between 1959 and 1976 abstained from alcohol after hospital discharge,20 36% of patients in a Danish study who received a hospital diagnosis of cirrhosis between 1993 and 2005 maintained abstinence,12 and 46% of participants in a UK study who were diagnosed with biopsy-proven alcohol-related liver cirrhosis between 1995 and 2000 reported abstinence both at 30 days post diagnosis and at follow-up a mean of 3.4 years later (although some admitted to lapses during that period). 21 However, the precise diagnosis given may influence subsequent drinking behaviour. Thus, Day26 studied 96 patients with biopsy-proven ALD referred to unit between August 1991 and August 1993: 76% had established cirrhosis or fibrosis, 23% had alcoholic hepatitis and 8% steatosis. At follow-up, 50% were still drinking heavily, although 21% were completely abstinent, and 21% had mild and 8% moderate alcohol intake. The only predictor of continued heavy intake was the absence of cirrhosis; continued heavy drinking was reported in 59% of patients without, and 38% of patients with, cirrhosis (p = 0.04). By contrast, a study of patients receiving liver transplants for ALD found that a number of factors were independently associated with a significantly increased risk of resumption of harmful alcohol consumption after transplantation: these were pre-transplant diagnosis of an anxiety or depressive disorder, a pre-transplant period of abstinence < 6 months, and a total score of > 3 on the high-risk alcoholism relapse (HRAR) scale (Table 1). Over a mean follow-up period of 61.2 months, the overall relapse rate was 11.9%; however, it varied from 5% to 100% depending on the number of relevant factors (Table 2). 27

It has therefore been suggested that, in patients with ALD, the degree of fibrosis may have less prognostic importance than other factors such as the severity of alcoholic hepatitis, severity of liver dysfunction as assessed by tools such as the Child–Pugh score, the MELD (Model for End-Stage Liver Disease) score, or the Glasgow score and subsequent drinking behaviour. 28

Significance for patients in terms of ill-health (burden of disease)

Alcohol-related liver disease is often asymptomatic. However, cirrhosis is associated with a number of complications, the more common of which include variceal bleeding, ascites, spontaneous bacterial peritonitis, and encephalopathy;41 these are associated with a significant burden of disease. Moreover, approximately 20% of patients with cirrhosis will go on to develop HCC (Dr Marsha Morgan, Royal Free Hospital, London, 2010, personal communication).

Portal hypertension is a major complication of chronic liver disease. It contributes to the development of ascites and HE, and forms a direct cause of variceal bleeding. Clinically significant PHt (i.e. PHt associated with a risk of such complications) has been defined as a HVPG measurement above about 10 mmHg. 42 Patients with clinically significant PHt should be offered treatment to reduce the risk of complications. 42

Approximately 40% of patients with liver cirrhosis have oesophageal varices, and approximately one-third of these will suffer variceal bleeding within 2 years of diagnosis. Such bleeding is associated with a mortality rate of 20–40% per episode43 and a 1-year mortality of 57%;4 nearly half of the deaths occur within 6 weeks of the initial episode of bleeding. 4

Over a 10-year period, approximately 50% of patients with compensated cirrhosis will develop ascites (excessive fluid within the peritoneal cavity). 44 This is associated with a poor quality of life, increased risk of infections, renal failure, and poor long-term outcomes. 45

Cirrhosis is also associated with HE, a condition that encompasses mental alterations ranging from mild (trivial lack of awareness, a shortened attention span, or euphoria or anxiety) to more obvious mental alterations including lethargy or apathy, occasional disorientation, personality change, and inappropriate behaviour, and in more severe cases to somnolence, confusion, gross disorientation and bizarre behaviour, and ultimately coma. Motor function is also impaired. 46 Patients who do not display any overt neurological abnormalities may nonetheless display subtle abnormalities of cognition and/or neurophysiological variables; this condition is termed minimal HE. Minimal HE appears to be associated with a reduction in health-related quality of life and in the ability to perform complex tasks such as driving a car. 46 It has been suggested that approximately 35–40% of cirrhotic patients will develop overt HE at some point, whereas approximately 20–60% with liver disease will develop minimal HE. 47

Diagnosis

The diagnostic pathways for suspected ALD are complex. Many people with ALD have no signs or symptoms of disease, the first indication of liver disease often coming from routine liver function tests. Others first come to medical attention when they report relatively mild symptoms (e.g. nausea, vomiting, abdominal discomfort, or diarrhoea). Sometimes, ALD is identified when people present voluntarily for detoxification, or when they require treatment for alcohol-related injuries or pneumonia, or alcoholic damage to organs other than the liver (e.g. the pancreas, heart, brain or peripheral nerves). 8 Yet other patients do not present until they have advanced liver disease characterised by more severe symptoms, such as jaundice, ascites, encephalopathy, or upper gastrointestinal bleeding. 8

The variability in the diagnostic pathways, caused by the varying reasons for presentation, is complicated by the absence of a single test that differentiates ALD from liver disease of other aetiologies. Rather, the patient’s history is obtained to identify risk factors (alcohol and other) for liver disease, and liver function tests, blood counts, and hepatitis serology are performed to exclude liver diseases of other aetiologies. 51 Ultrasound may also be used. 9 Because patients without clinical evidence of decompensated cirrhosis may have histologically advanced ALD but normal, or only mildly abnormal, liver function test results, liver biopsy may be required to confirm the diagnosis and the stage of the disease by assessing the degree of fibrosis. 9,52

There is a lack of consensus about the role and the timing of biopsy in patients with suspected ALD. 51 This derives in part from the absence of high-quality evidence for the accuracy of liver biopsy specifically in the diagnosis of ALD, together with the fact that its status as the ‘gold standard’ diagnostic and staging tool has been called into question for several reasons. There are also concerns relating to the safety of liver biopsy. For further details, see Summary of diagnostic tests.

Management of disease

Following a diagnosis of ALD, the aims of management are to treat the underlying cause, prevent disease progression, and manage complications. By far the most important management aim in all patients is to ensure long-term abstinence from alcohol. As noted in Aetiology, pathology and prognosis, a small UK study found that ≤ 50% of patients with ALD either abstained completely from alcohol or significantly reduced their intake following simple advice from a physician during their initial presentation. 26 Additional pharmacological or non-pharmacological interventions may also be used to promote abstinence. 8,52 Other aspects of management include lifestyle changes to reduce cigarette consumption and obesity,10 if relevant.

In patients with relatively mild alcoholic hepatitis, the focus of treatment is the achievement of abstinence. Corticosteroid therapy may be used to treat severe AAH,9 but there is no conclusive evidence that it leads to significant improvements in survival. 53 As most patients with AAH have some degree of malnutrition, nutritional therapy may also be offered. 25

A range of therapies may be used to treat the various complications of alcoholic cirrhosis. 8,52 Complications such as fluid retention, HE, and variceal bleeding are treated symptomatically. Because prophylactic treatment with non-selective beta-blockers or band ligation reduces the risk of first bleeding in patients with medium or large varices by 50%, all patients with cirrhosis should be screened regularly by endoscopy for signs of PHt (particularly the presence of oesophageal varices), and, if necessary, offered preventative treatment against gastrointestinal bleeding. Current guidance recommends that all patients diagnosed with cirrhosis should be offered such endoscopic screening every 2 years if they have no varices and annually if they have small varices54 or decompensated disease with or without varices. 42 Abdominal Doppler ultrasound may be used to screen for liver and portal abnormalities (especially HCC). 11

Orthotopic liver transplantation has a place in the management of patients with decompensated alcohol-related cirrhosis who have failed to improve despite well-documented abstinence from alcohol and expert medical treatment for a period of approximately 6 months. Survival rates are similar to those observed in patients transplanted for non-alcoholic cirrhosis, although recidivism rates are still unacceptably high in some centres. Transplantation is also considered the optimal treatment for early HCC. 55 However, the supply of donor livers is limited. 8

The Enhanced Liver Fibrosis Test

The Enhanced Liver Fibrosis Test is a blood test that uses an algorithm combining three biomarkers [hyaluronic acid (HA), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and aminoterminal propeptide of procollagen type III (PIIINP)] to assess the stage and rate of progression of liver fibrosis. 57 The biomarkers are direct markers of extracellular matrix metabolism/degradation indicative of liver fibrosis. A higher concentration of the individual biomarkers leads to a higher ELF score and indicates a higher probability of more severe fibrosis.

The test requires a minimum of 0.3 ml of serum. 58 Blood samples are collected in a clinic and analysed at a central laboratory. 51

As alcohol affects many of the variables used in the ELF test,59,60–62 individuals should ideally be abstinent before the blood sample is taken.

The ELF test was CE marked in May 2007. 51

FibroTest and FibroMAX

FibroTest and FibroMAX are proprietary algorithms that use serum biochemical markers to assess the stage of liver fibrosis. 64 FibroTest (marketed in the USA as FibroSure) combines one direct marker of extracellular matrix metabolism/degradation (alpha-2-macroglobulin) and four indirect markers (apolipoprotein A1, haptoglobin, total bilirubin and gamma-glutamyl transpeptidase) with the patient’s age and sex. 65

Blood samples are not analysed at a central laboratory, but it is recommended that the individual components of the test are analysed using the same techniques and analysers as used by the reference laboratory that developed FibroTest. 66 The individual values are then entered into BioPredictive’s website (www.biopredictive.com) and an algorithm calculates the results, which are presented as numeric estimates on a continuous scale ranging from 0.00 to 1.00. Table 8 displays the correspondence proposed by Morra et al. 67 between FibroTest scores and the fibrosis stages identified by the METAVIR, Knodell, and Ishak fibrosis staging systems.

FibroMAX combines the components of FibroTest with alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, fasting blood glucose, height and weight, and presents on one sheet the scores for FibroTest, SteatoTest (which measures hepatic steatosis) and AshTest (which measures the degree of necroinflammatory activity of alcoholic origin). 68

FibroTest and FibroMAX are validated for use in patients with chronic viral hepatitis (B or C), ALD, and non-alcoholic fatty liver disease (NAFLD). The manufacturer recommends the use of FibroTest in patients with hepatitis B or C and FibroMAX in those with alcoholic or metabolic liver disease. 69

Although FibroTest may be performed on blood samples from fasting or non-fasting patients, FibroMAX must be performed on samples from fasting patients. 67 As in the case of the ELF test, alcohol affects many of the variables used in FibroTest; therefore, individuals should ideally be abstinent before the blood sample is taken (Dr Marsha Morgan, Royal Free Hospital, London, 2010, personal communication).

FibroTest and FibroMAX are said to yield consistent results, with a reproducibility > 95%. 70,71 However, this has been questioned. A small study by Gressner et al. 72 suggests that FibroTest scores may vary by up to two METAVIR stages as a result of possible interlaboratory differences in measurements of the individual test components, even when the laboratories fulfil BioPredictive’s technical requirements and the measurements lie within a quality-controlled, analytically acceptable range. Moreover, Poynard et al. ’s73 prospective analysis of discordance between the FibroTest and biopsy results in patients with hepatitis C demonstrated that critical interpretation of every FibroTest result is required in order to avoid false-positive (FP) or false-negative (FN) results.

The FibroTest and FibroMAX algorithms are patented, but not CE marked; they have not been published. 66 However, there are CE-marked kits for assessing the individual components.

FibroScan

FibroScan is produced by EchoSens, Paris, France, and distributed in the UK by Artemis Medical Ltd., Kent, UK75 It is a non-invasive test that uses a specialised probe, an ultrasound and elastography system, and specialised software. The probe is placed on the skin over the right lobe of the liver and generates a mechanical pulse that sends a shear wave to the liver through the intercostal spaces. 76,77 The wave’s velocity is measured by ultrasound and is determined by the stiffness of the liver, which is correlated with the degree of fibrosis. 76

The procedure, which is painless, can be performed by trained medical or paramedical staff. Each test typically takes < 15 minutes. 75 The result is the median of 10 individual ‘shots’, reported as a numerical measure in kilopascal (kPa);78 it is available immediately. 76 If a shot is unsuccessful, the machine provides no result and the whole process is deemed to have failed if no value is obtained after ≥ 10 shots. 79 In addition, the manufacturer recommends that, to be considered reliable, successful measurements should meet the following three criteria:

• at least 10 valid shots

• a success rate (the ratio of valid shots to total number of shots) of at least 60%

• an interquartile range < 30% of the median value. 79

FibroScan values range from 2.5 to 75 kPa; normal values are around 5.5 kPa. 80 A cut-off value of about 12.5 kPa has been proposed as optimal for discriminating between fibrosis and cirrhosis in patients with chronic hepatitis C. 81 As the threshold for cirrhosis appears to be higher in patients with ALD, it is important that disease aetiology should be established before testing.

FibroScan is claimed to measure liver stiffness in a cylinder approximately 1 cm in diameter and 4 cm long, between 25 and 65 mm below the surface of the skin. 82 The volume of this cylinder is at least 100 times that of a percutaneous liver biopsy sample, and is therefore far more representative of the whole liver, reducing the risk of sampling error. However, the claim that it may be performed satisfactorily on non-fasting patients82 has recently been called into question by the finding that liver stiffness values increase substantially after food intake in both patients with hepatitis C infection and healthy controls. 83

FibroScan appears to have good reproducibility. In a series of 195 patients with chronic liver disease of various aetiologies and without ascites, using the FibroScan ultrasonography guide to identify a suitable portion of the liver for examination, Fraquelli et al. 84 found that overall agreement between two operators was 0.98 [95% confidence interval (CI) 0.977 to 0.987], and intraobserver agreement was 0.98 for both operators. Increased BMI (> 25 kg/m²), steatosis (> 24% of fatty liver cells), and histological evidence of no to mild fibrosis (METAVIR stage < F2) were all significantly associated with reduced interobserver agreement, and the most marked variability was seen in mild fibrosis (F0/F1), where interobserver agreement fell to 0.60 (95% CI 0.455 to 0.719).

FibroScan is CE marked. Because it is designed specifically to test for liver fibrosis, and does not produce an image, it cannot be used for any other diagnostic purpose. 56

Liver biopsy

The true gold standard for assessing the degree of liver fibrosis is histological analysis of the whole liver. As this is not possible in living patients, liver biopsy has been adopted as the reference standard.

Liver biopsy has a number of disadvantages. It is an invasive test: a hollow needle is used to remove a small sample of tissue from the patient for examination in the laboratory. It is performed in the fasting patient and is generally preceded by ultrasonography of the liver. 86 In most cases, liver biopsy is performed percutaneously, through the skin over the liver. However, in order to reduce the risk of complications associated with bleeding, it may be performed transvenously in patients with conditions such as ascites or coagulation defects, which are relatively common in ALD, and which form contraindications to percutaneous biopsy. In transvenous biopsy, a catheter carrying the biopsy needle is inserted through a vein (most commonly the jugular vein in the neck) and guided to the veins inside the liver. 87 Liver biopsy is also occasionally performed laparoscopically. 9

Liver biopsy often involves a hospital stay. Patients should undergo liver biopsy on an outpatient basis only if they have no conditions that may increase the risk of the procedure, and then only in locations with easy access to a laboratory, blood bank, and inpatient facilities, and with staff who can observe the patient for 6 hours following the procedure. In addition, the patient should be able to return easily within 30 minutes to the hospital where the biopsy was undertaken, and should have a reliable individual to stay with on the first night post biopsy. If any of these criteria cannot be met, biopsy must be undertaken on an inpatient basis. Moreover, patients who undergo outpatient biopsy should be hospitalised if there is any significant complication, including pain that requires more than one dose of analgesic. 88 In the USA, where liver biopsy is generally performed on an outpatient basis under local anaesthetic, 1–3% of patients subsequently require hospital care for the management of complications (predominantly pain or hypotension); 60% of these complications occur within 2 hours of the biopsy and 96% within 24 hours. 86

Because fibrosis is not evenly distributed throughout the liver, liver biopsy, which samples only 1/25,000–50,000 of the liver, carries a substantial risk of sampling error. Regev et al. 89 found a difference of at least one fibrosis stage between biopsy samples from the right and left hepatic lobes in 33% of patients with hepatitis C. Such sampling errors usually produce a low FP rate but a relatively high FN rate but, in the case of liver biopsy, inclusion of elements such as capsular or connective tissue will lead to overestimation of the degree of fibrosis. 16 Factors that affect the degree of sampling error include the length of the biopsy sample and the number of samples taken. Bedossa et al. 90 demonstrated experimentally in liver samples from patients with hepatitis C that correct staging was achieved for only 65% of cases when the biopsy sample was 15 mm in length; this figure rose to only 75% when samples 25 mm in length were analysed, and the proportion of samples which were correctly identified did not increase significantly with longer specimens. Abdi et al. 91 found that a single biopsy correctly identified cirrhosis in only 80% of cases (16/20) at post-mortem, but that 100% accuracy was achieved when three samples were taken,91 while Maharaj et al. 92 also found that a single sample was unreliable: when three consecutive samples were taken through a single entry site, all three samples identified cirrhosis in only 50% of cases.

In addition to sampling error, liver biopsy results may be affected by intra- and inter-pathologist variation in the interpretation of samples. 93 Levels of inter- and intra-observer discrepancies as high as 10–20%89,94 have been reported.

However, liver biopsy has the advantage that it provides information not only on liver fibrosis but also on other factors such as inflammation, necrosis, and steatosis, and permits the identification of potentially unexpected cofactors and comorbidities. 95

Hepatic venous pressure gradient measurement

Hepatic venous pressure gradient measurement is the gold standard for assessing the presence and severity of PHt in patients with alcohol-related cirrhosis, in whom splenomegaly, the clinical hallmark of PHt, is a less useful sign. HVPG measurement is an invasive procedure in which a balloon-tipped catheter is inserted into a hepatic vein via the femoral or jugular route. The pressure is measured with the balloon deflated, and again when it has been inflated to occlude the hepatic vein. The HVPG is the difference between the two measurements; a result > 5 mmHg indicates PHt, and a result > 10–12 mmHg indicates clinically significant PHt associated with a risk of complications such as ascites, HE, and variceal bleeding. 42

Hepatic venous pressure gradient measurement is reliable only when performed by an experienced operator. 97

Upper gastrointestinal endoscopy

Upper gastrointestinal endoscopy involves the insertion of a thin, flexible viewing instrument, called an endoscope through the mouth into the oesophagus, stomach, and duodenum. It is used in patients with cirrhosis to identify medium or large varices in those areas so that prophylactic treatment may be initiated to reduce the risk of bleeding.

Endoscopy is expensive to perform. 99 Patients must have had nothing to eat or drink for 4–8 hours prior to the procedure.

Discussion of outcomes measuring test accuracy

In studies of diagnostic tests, patients are generally classified by the index test (i.e. the diagnostic test being investigated) as either positive or negative (i.e. as having or not having the condition that the test is designed to identify). The same patients are also assessed using the reference standard (an established diagnostic test assumed to have 100% sensitivity and specificity), and the latter result is taken to identify the patients’ true health status. If both the index test and the reference standard are positive, the result is described as a TP. If the index test is positive but the reference standard is negative, the result is termed a FP. If both the index test and the reference standard are negative, the result is termed a TN, whereas if the index test is negative and the reference standard is positive it is termed a FN. These results can be presented in a 2 × 2 table (Table 9).

The sensitivity of a test (the proportion of patients with the condition of interest who have a positive test result – i.e. TPs), indicates how good it is at correctly identifying the condition of interest, whereas its specificity (the proportion of patients without the condition of interest who have a negative test result – i.e. TNs) indicates how good it is at correctly classifying people as free of that condition. The sensitivity and specificity are expressed as simple percentages (see Table 9). Both FP and FN results may be harmful: FP results may cause patients to undergo further tests or receive unnecessary treatment, whereas FN results may deprive them of the treatment they need. Ideally, therefore, diagnostic tests would have both high sensitivity and high specificity. In practice, however, they often have high sensitivity at the expense of low specificity or vice versa. The optimum balance between sensitivity and specificity varies from test to test because of differences in the relative consequences of FP and FN results in the context of the condition of interest.

In practice, the situation may be more complex than indicated in Table 9, as the results of the index test may be neither positive nor negative, but uninterpretable. It is important that such uninterpretable results should be included in the calculations. Their inclusion will lower the sensitivity and specificity of the index test (Table 10). In the absence of full data relating to uninterpretable results, sensitivity analyses may be used to explore the impact of such results on sensitivity and specificity.

The positive predictive value of a test is the proportion of patients with positive test results who are correctly diagnosed. In clinical practice, this is generally the most important measure of test accuracy as it reflects the probability that a positive test reflects the underlying condition being tested for. Consequently, its value depends on the prevalence of the disease, which may vary, and indeed in real life situations may differ considerably from that seen in study populations. The negative predictive value is the proportion of patients with negative test results who are correctly diagnosed. The negative predictive value may be more important than the positive predictive value if the test is being used as a triage test to identify those patients who may have the condition of interest so that they may undergo further, more expensive or invasive, testing.

Although fibrosis has, for convenience, been divided into grades of severity using a number of different scales, the most common being the METAVIR scale (see Chapter 1, Measurement of disease), it actually forms a continuum that ranges from very mild fibrosis to severe fibrosis (cirrhosis). Consequently, the non-invasive tests for fibrosis reviewed in this report also yield continuous measurements and, therefore, diagnostic thresholds must be deliberately selected to define positive and negative results. The sensitivity and specificity of the tests will vary depending on the thresholds that have been selected. If several thresholds have been used in one data set, the diagnostic characteristics of the test in question may be illustrated using a receiver operating characteristic plot of the TP rate (sensitivity) against the FP rate (1 – specificity). 103

The AUROC may be used as an overall measure of the performance of a surrogate test when compared with the reference standard. Bedossa and Carrat104 state that the AUROC represents the probability that the surrogate will correctly rank two randomly chosen patients, one of whom has been classified by the reference standard as having, and the other as not having, the condition that the index and reference tests are intended to identify. Unlike sensitivity and specificity, the AUROC does not vary according to the threshold set for identification of a positive result. It therefore represents a loss of information, as compared with sensitivity and specificity, as it provides no indication of the degree to which any departure from 1.00 (a perfect result) is because of FPs, and the degree to which it is because of FNs. Moreover, Lambert et al. 105 have noted that, in the context of liver fibrosis, the AUROC has two main drawbacks:

• Because it assumes that the reference standard yields a binary result whereas, as has been seen, liver biopsy uses an ordinal scoring system, the fibrosis stages have to be aggregated into two groups.

• Because the proportion of each fibrosis stage in the sample can affect the AUROC, comparisons of AUROCs from populations with different distributions of fibrosis stages may be flawed. To overcome this, Poynard et al. 106 recommend standardising the AUROC according to the prevalence of fibrosis stages, but this method is complex and has not yet been statistically validated. 105

As noted above, calculation of the sensitivity and specificity of the index tests involves the assumption that the reference standard has 100% sensitivity and specificity. Unfortunately, this is not true of liver biopsy (see Chapter 1, Summary of diagnostic tests). If the results of the reference test are not very close to the truth, the performance of the index tests will be poorly estimated. 103 In an attempt to address this problem, a number of the studies included in this review have looked in detail at cases in which the index test and reference standard have yielded discrepant results, to determine which test is more likely to have provided the correct result in each individual case.

Another serious problem relating to the use of liver biopsy as the reference standard is its relevance to the different types of non-invasive tests. On the one hand, liver biopsy is arguably a more appropriate reference standard in relation to transient elastography than in relation to tests based on serum markers because it seeks directly to identify the degree of fibrosis present in the liver at a fixed point in time, whereas transient elastography measures the stiffness of the liver, a surrogate for fibrosis, also at a fixed point in time. By contrast, tests such as the ELF test and FibroTest, which are based on combinations of serum markers, seek to assess dynamic processes taking place within the liver. Consequently, their results may be discordant with the liver biopsy results either because the fibrotic process is highly active but fibrotic tissue has not yet developed (thus the serum tests will yield a higher result than the biopsy), or because fibrotic activity is temporarily discontinued even though there are clusters of fibrotic tissue in the liver (thus the serum tests will yield a lower result than the biopsy). 107 In such circumstances, the test results may be discordant even though both tests have yielded correct results in terms of the parameter that they set out to measure. On the other hand, it has been argued that liver biopsy is a more appropriate reference standard in relation to serum marker algorithms such as FibroTest and the ELF test, which have been designed to match histological stages of liver fibrosis as assessed by liver biopsy irrespective of biopsy accuracy, than in relation to transient elastography, which measures stiffness, a single genuine characteristic of liver tissue. 104

Sources searched

The electronic databases searched included MEDLINE, EMBASE, The Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and Web of Knowledge (for details, see Appendix 5).

Search strategies

The MEDLINE search strategies are presented in Appendix 5. Search strategies for the other databases are available on request.

Search restrictions

Searches were not restricted by publication type, date of publication, or language.

Inclusion criteria

• Participants: Patients with suspected liver fibrosis related to alcohol consumption. Studies that included patients with suspected liver fibrosis of other aetiologies were included if data relating to patients with suspected alcohol-related disease could be extracted separately.

• Intervention: One of the specified non-invasive tests for liver fibrosis, namely:

  1. – the ELF test

  2. – FibroTest

  3. – FibroMAX

  4. – FibroScan.

• Comparators: The primary comparator, or reference standard, was liver biopsy for the identification of liver fibrosis. Secondary reference standards were tests used to identify conditions associated with liver fibrosis, namely HVPG measurement for PHt, and upper gastrointestinal endoscopy for the identification of oesophageal varices.

• Outcome measures: The primary outcome measure was the diagnostic accuracy of the index test compared with the reference standard in distinguishing patients with significant fibrosis, defined as METAVIR stages F2–F4, from patients without significant fibrosis, defined as METAVIR stages F0–F1. Other outcome measures were:

  1. – the diagnostic accuracy of the index test compared with the reference standard in distinguishing patients with cirrhosis (METAVIR stage F4) from patients without cirrhosis (METAVIR stages F0–F3)

  2. – the diagnostic accuracy of the index test compared with the reference standard in distinguishing patients with moderate-to-severe fibrosis (METAVIR stages F3–F4) from patients without moderate-to-severe fibrosis (METAVIR stages F0–F2)

  3. – the diagnostic accuracy of the index test compared with the reference standard in distinguishing patients with fibrosis (METAVIR stages F1–F4) from patients without fibrosis (METAVIR stage F0)

  4. – the diagnostic accuracy of the index test compared with the reference standards in distinguishing patients with and without the complications of fibrosis (PHt and oesophageal varices)

  5. – the number of patients requiring referral to secondary care

  6. – the number of patients requiring liver biopsy

  7. – the number of patients giving up alcohol, or significantly reducing alcohol consumption, following receipt of a test result

  8. – long-term patient outcomes (disease progression, complications related to liver disease, need for liver transplantation, mortality)

  9. – adverse effects of testing

  10. – health-related quality of life.

Only studies of the index tests that reported data relating to one of the outcome measures in relation to the population of interest were included in the review of clinical effectiveness. However, this criterion was relaxed for consideration of adverse events, where wider searches were undertaken to allow the inclusion of data relating to studies of the adverse effects of diagnostic venepuncture or transient elastography (see Appendix 5).

• Study design: the best available level of evidence, with priority given to controlled studies, if available.

Exclusion criteria

The following publication types were excluded from the review:

• animal models

• preclinical and biological studies

• narrative reviews, editorials, and opinions.

Systematic reviews of primary studies were excluded from the review of clinical effectiveness, but were scanned for potential additional relevant studies.

In addition, studies were excluded if:

• they were considered methodologically unsound (specifically, if the reference standard was used in only a subset of study participants and the selection criteria used to identify that subset were not clear)

• they were published as meeting abstracts only, and insufficient methodological details were reported to allow critical appraisal of study quality

• they were meeting abstracts that had been superseded by later publications and did not contain any additional data.

Sifting

The references identified by the literature searches were sifted in three stages by a single reviewer. They were screened for relevance first by title and then by abstract. Those papers that seemed, from their abstracts, to be relevant were then read in full, as were all potentially relevant papers for which abstracts were not available. At each step, studies that did not satisfy the inclusion criteria were excluded.

Number and type of studies included

The majority of articles that met the review inclusion criteria reported cross-sectional studies intended to confirm the performance of one of the non-invasive tests against a reference standard (liver biopsy, HVPG measurement, or endoscopic identification of oesophageal varices). A minority had a cohort design, following patients over time to assess how well the non-invasive test predicted adverse clinical outcomes. There were no randomised controlled trials (RCTs).

Number and type of studies excluded, with reasons

As may be seen from Quantity and quality of research available, a substantial number of the citations identified by the electronic searches related to studies that were excluded as part of the sifting process because they did not meet the inclusion criteria. Details are therefore given only of those citations that were excluded after a full reading, and then only if they were excluded for a reason other than a simple failure to meet the inclusion and exclusion criteria. Such citations are listed in Appendix 7, together with the reasons for their exclusion.

Study characteristics

Study quality

Figures 5–9 provide an overview of the methodological quality of the included studies.

FIGURE 5.

The ELF test: methodological quality summary. Review authors’ judgements about each methodological quality item. –, no; +, yes; ?, unclear.

FIGURE 6.

FibroTest: methodological quality graph. Review authors’ judgements about each methodological quality item presented as percentages across all included studies.

FIGURE 7.

FibroTest: methodological quality summary. Review authors’ judgements about each methodological quality item for each included study. –, no; +, yes; ?, unclear.

FIGURE 8.

FibroScan: methodological quality graph. Review authors’ judgements about each methodological quality item presented as percentages across all included studies.

FIGURE 9.

FibroScan: methodological quality summary. Review authors’ judgements about each methodological quality item for each included study. –, no; +, yes; ?, unclear.

As may be seen, few studies presented results relating to a representative spectrum of patients suspected of having ALD. The majority recruited patients with relatively severe disease. Bureau et al. ,129 Rosenberg et al. 121 and Thabut et al. 2007a13 recruited patients who were due to undergo liver biopsy for clinical reasons, whereas Lemoine et al. ,97 Nguyen-Khac et al. 130 and Thabut et al. 2007b126 recruited patients known to have cirrhosis, Naveau et al. 123 recruited patients hospitalised for complications of cirrhosis or alcoholism, and Mueller et al. 118 and Thabut et al. 2003126 recruited those known to have, rather than suspected of having, chronic liver disease. Two studies, those by Janssens et al. 117 and Melin et al. ,122 recruited more representative populations, but displayed partial verification bias, using the reference standard only in patients scoring above a specific threshold on the index test (FibroScan in both cases).

In studies of test accuracy, it is clearly important that the interval between the performance of the index and reference tests should be as short as possible, to minimise the possibility of the patient’s condition altering significantly between the tests. However, several studies allowed a delay of > 2 weeks between the index test and reference standard. Naveau et al. 123 allowed an interval of up to 1 month, whereas Kim et al. 127 allowed the interval between transient elastography and liver biopsy to be as much as 92 days, and Thabut et al. 2003125 included patients in whom endoscopy was performed up to 6 months before or after FibroTest, although in this case the mean interval was only 5 days.

In approximately half of the included studies, it was not clear whether the reference standard results were interpreted without knowledge of the results of the index test (‘reference standard results blinded’) and vice versa (‘index test results blinded’). The remaining studies stated that blinding was used for either one or both tests. The index test was usually well described, but in many cases the execution of the reference standard was not described in sufficient detail to permit replication of the test precisely as performed by the study investigators.

Uninterpretable/intermediate results were generally poorly reported. Two studies, Rosenberg et al. ’s121 study of the ELF test and Lemoine et al. ’s97 FibroScan study, stated that patients were recruited prospectively and consecutively, and reported no uninterpretable/intermediate results, implying that there were none. Bureau et al. ’s129 FibroScan study reported the overall number of uninterpretable results, but did not specify how many related to patients with ALD; it is not clear whether or not they were included in the analyses. Janssens et al. ,117 Kim et al. ,127 Melin et al. ,122 Mueller et al. ,118 Nahon et al. 128 and Nguyen-Khac et al. 132 all reported the number of instances of FibroScan failure (i.e. no or uninterpretable results), but did not include them in their analyses. As none stated how many of these failures occurred in patients who tested positive and how many in patients who tested negative by the reference standard, their impact on test sensitivity and specificity could not be calculated.

The three tests for which evidence has been identified vary in the extent to which that evidence is independent of the test manufacturer. There is no wholly independent evidence relating to the ELF test: one of the investigators, Professor William Rosenberg, is the founder of, and holds stocks in, iQur Ltd, which holds a limited licence to conduct ELF assays on behalf of Siemens Healthcare Diagnostics. 57 Only one of the studies of FibroTest, that by Nguyen-Khac et al. ,132 appears to be independent. The remaining studies include in their authorship Thierry Poynard, a major stockholder in, and Mona Munteanu, an employee of, the manufacturers, BioPredictive. 125 However, six of the nine studies that provided data relating to FibroScan97,117,128–130,132 stated that the authors had no conflicts of interest in relation to the work; of the studies that did not include such a declaration, that by Mueller et al. 118 stated that it was funded from independent sources, and only the studies by Kim et al. 127 and Melin et al. 122 contained no relevant information on this point.

Two further indices of methodological quality proposed by Tsochatzis et al. 138 were not included in the QUADAS checklist as they were not applicable to all of the included studies. These were:

• whether studies that used liver biopsy as the reference standard reported that it was performed to an acceptable standard (i.e. the specimen was at least 15 mm long and included at least six portal tracts)

• whether studies of FibroScan reported that it was performed in accordance with the manufacturer’s instructions, i.e. using at least 10 valid shots, with a success rate (ratio of valid shots to total number of shots) of at least 60%, and an interquartile range < 30% of the median value. 79

Only one study that used liver biopsy as a reference standard reported using adequate criteria; this was the study by Janssens et al. 117 This was also one of only two studies which clearly stated that FibroScan was performed either in accordance with the manufacturer’s instructions or, in the case of the study by Lemoine et al. ,97 using more stringent criteria. The remaining studies failed either to meet or, more frequently, to report one or more of the standards (for details, see Table 14).

Enhanced Liver Fibrosis Test: diagnostic and prognostic accuracy results

The evidence base for the ELF test is small, resting on a single study of the European Liver Fibrosis Test carried out in a population with chronic liver disease that included < 100 patients diagnosed with ALD. Moreover, the quality of that evidence is not ideal as liver biopsy was not performed to an acceptable standard (see Study quality).

This limited evidence suggests that the ELF test can generally distinguish patients with moderate-to-severe fibrosis (Scheuer stages 3–4) from those with milder or no fibrosis (Scheuer stages 0–2) in patients with ALD. Using a low threshold score of 0.087, the test showed 100% sensitivity, but only 16.7% specificity. Ninety-three per cent sensitivity and 100% specificity were achieved using a threshold score of 0.431 (Table 15). These threshold scores appear to have been derived from the AUROCs after data collection, rather than prospectively selected and validated. As the the investigators note, because the results rest on data from so few patients, the resulting positive and negative predictive values should be interpreted with caution. 121

The ELF test appears to be less successful in distinguishing patients with probable or definite cirrhosis (Scheuer stage 4) from those with milder or no fibrosis (Scheuer stages 0–3) (see Table 15). As this result was only presented in the form of an AUROC, the sensitivity and specificity associated with a specific threshold score or scores could not be calculated. Discordant results were not discussed for either fibrosis range.

The evidence relating to the prognostic accuracy of the ELF is derived from data from 85 patients with ALD who were enrolled in the European Liver Fibrosis Test study in English centres and were followed up over a median period of 6.86 years (range 0–9 years). Thus, as for test accuracy, the evidence base is very small. During the follow-up period, 27 patients (32%) died of liver-related causes, a further seven (8%) suffered non-fatal liver-related clinical events, and seven (8%) died of non-liver-related causes. 57 Again, results are only presented in the form of an AUROC. Although this suggests that the ELF is predictive both of liver-related clinical outcomes and of all-cause mortality (for details, see Table 15), it should be noted that the sensitivity and specificity associated with a specific threshold score or scores could not be calculated and, more importantly, no information was presented on post-test alcohol consumption, although is likely to have been a substantial confounding factor.

FibroTest: diagnostic and prognostic accuracy results

The evidence base for FibroTest, although more substantial than that for the ELF test, derives from a total of only 622 patients enrolled in five small to medium-sized studies; although the evidence for test accuracy relative to liver biopsy is derived from a total of only 390 patients enrolled in three of those studies, none of which state that they stipulated a minimum biopsy length of 15 mm.

The available evidence suggests that FibroTest can distinguish between patients with cirrhosis and those with METAVIR stage F0–F3 fibrosis, and, with lesser accuracy, between those with stage F2–F4 and stage F0–F1 fibrosis, and between those with stage F3–F4 and stage F0–F2 fibrosis (Table 16). However, not only are these conclusions based on data from only three relatively small studies,13,123,132 in which some biopsy samples may not have met the recommended minimum standards, as noted above, but the prevalence of the condition of interest was high in each of the three studies, ranging from 63% to 98% for METAVIR stage F2–F4 fibrosis, 51% for METAVIR stage F3–F4 fibrosis, and from 31% to 92% for cirrhosis.

The largest study of test accuracy relative to liver biopsy, that by Naveau et al. ,123 also had the most representative population in that it included the lowest proportion of patients with F2–F4 fibrosis. It explored the impact of different threshold scores on sensitivity and specificity. At a threshold score of 0.30, FibroTest had reasonable sensitivity, but rather disappointing specificity in relation to moderate-to-severe (F2–F4) fibrosis; this situation was reversed when the threshold score was raised to 0.70. For cirrhosis, a threshold score of 0.30 produced 100% sensitivity but only 50% specificity, and the balance was improved using a threshold score of 0.70 (for details, see Table 16). Thabut et al. 2007a13 found that, at a threshold of 0.48, the specificity of FibroTest in relation to moderate-to-severe (F2–F4) fibrosis was 0% because the prevalence of that condition in the study population, as indicated by liver biopsy, was 98%. Similarly, although FibroTest displayed a sensitivity of 95% for the diagnosis of F2–F4 fibrosis, this result is not robust because 92% of the study population had biopsy results indicative of cirrhosis. The third study of test accuracy relative to liver biopsy, that by Nguyen-Khac et al. ,132 did not indicate what diagnostic thresholds were used; it did not report sensitivity and specificity, and the underlying data that would have allowed them to be calculated could not be obtained.

Both Naveau et al. 123 and Thabut et al. 2007a13 provided some discussion of discordant cases. Naveau et al. 123 reported a discordance of two or more fibrosis stages in 19% of assessed patients (42/221). On the basis of independent clinical, ultrasonographical, and endoscopic signs of cirrhosis, they attributed the error to the biopsy in 26 cases (14 FNs and 12 FPs), and to FibroTest in 13 cases (six FNs and seven FPs); three cases were unattributable. 123 Eighteen of the 42 discordant cases involved diagnoses of cirrhosis: three FNs and three possible FPs of FibroTest, three FPs and eight possible FNs of biopsy (the eight FNs of biopsy were all in poor-quality samples), and one unattributable case diagnosed as cirrhosis by FibroTest but not by biopsy. 123

Thabut et al. 2007a13 attributed discordant cases to failure of biopsy or FibroTest on the basis of clinical events (haemorrhage, ascites) and risk factors for FibroTest failure. Four of the 61 patients with cirrhosis (7%) had FN results on FibroTest; all had large ascites and low alpha-2-macroglobulin. No other discordant results were reported. 13

Two small studies by Thabut et al. (2007a and 2003),13,125 which included only 66 and 58 patients with ALD, respectively, suggest that FibroTest can also distinguish between patients with and without PHt and, with less accuracy, between those with and without oesophageal varices. However, these studies were also carried out in populations with a high prevalence of those conditions, and indeed the investigators noted that, as 86% of the population of Thabut et al. ’s 2007a study13 had HVPG results indicating clinically significant PHt (HVPG > 12 mmHg), the study findings should not be used as a basis for recommending the use of FibroTest alone to predict severe PHt in cirrhotic patients.

The study by Naveau et al. 124 and, to a lesser extent, that by Thabut et al. 2007b126 suggest that FibroTest may also be able, with relatively low accuracy, to predict liver-related mortality and all-cause mortality (see Table 16). In Naveau et al. ’s124 cohort study, 85 patients (39%) died during the follow-up period: 42 (19%) of liver-related causes (haemorrhage, HCC, and decompensation) and 43 (20%) of non-liver-related causes. FibroTest was predictive of survival or non-liver-related mortality and, to a lesser degree, of overall mortality (for details, see Table 16). Details of 5- and 10-year survival according to baseline FibroTest values are presented in Tables 17 and 18. The baseline FibroTest and biopsy results were concordant for 38 (90%) of the 42 liver-related deaths (29 with cirrhosis, nine without cirrhosis) and discordant for only four (10%; two FPs of FibroTest, and one FP and one FN of biopsy). 124

Naveau et al. ’s124 cohort study also provided information on subsequent alcohol consumption in patients enrolled in their 2005 study of test accuracy. 124 Only 21% (46/218) were known to be abstinent during the follow-up period; 50% (108/218) were not abstinent, and the status of the remaining 29% (64/218) was not known. 124 Unfortunately, the authors did not link these data with test results, and thus it was not possible to determine whether or not the test results had an impact on subsequent alcohol consumption, or whether or not alcohol consumption affected survival.

FibroScan: diagnostic accuracy results

The evidence base for FibroScan is slightly larger than that for FibroTest, deriving from a total of approximately 868 patients enrolled in nine small to medium-sized studies (the total number of participants is approximate because, as indicated in Table 13, it is not always clear how many of the eligible patients were in fact assessed). The evidence for test accuracy relative to liver biopsy is derived from a total of only 480 patients enrolled in the studies by Janssens et al. ,117 Kim et al. ,127 Melin et al. ,122 Mueller et al. ,118 Nahon et al. ,128 and Nguyen-Khac et al. 132 In only one of these, that by Janssens et al. ,117 are the liver biopsy samples known to have met the recommended minimum standards.

The evidence that FibroScan can distinguish patients with METAVIR stage F1–F4 fibrosis from those without fibrosis (F0), and those with F2–F4 fibrosis from those with stage F0–F1, is not robust, being based on only one fairly small study by Nguyen-Khac et al. 132 in a population with a high prevalence of stage F2–F4 fibrosis. However, there is more substantial evidence that FibroScan can distinguish patients with stage F3–F4 from those with stage F0–F2 fibrosis, and those with cirrhosis from those with stage F0–F3 fibrosis (Table 19).

The data presented in Table 19 illustrate the impact of different threshold scores on the sensitivity and the specificity of FibroScan. Castéra et al. 81 originally suggested that, in patients with chronic hepatitis C, the optimal FibroScan threshold values for the identification of significant (F2–F4) fibrosis, advanced (F3–F4) fibrosis, and cirrhosis (F4) were 7.1, 9.5, and 12.5 kPa, respectively (Table 20). These values were used by some of the studies included in this review and were found to be less appropriate for use in patients with ALD. Melin et al. 122 achieved 100% sensitivity using a threshold score of 13 kPa to identify cirrhosis in patients with ALD, but could not estimate the specificity associated with this threshold because patients with a score < 13 kPa did not undergo liver biopsy. Other investigators specifically sought to identify the optimal threshold scores for use in patients with ALD (see Table 19). Janssens et al. 117 noted that, in such patients, the threshold score of 9.5 kPa proposed for hepatitis C had 100% sensitivity for identifying severe (F3–F4) fibrosis, but a PPV of only 65%; it overestimated the degree of fibrosis in 17 of the 49 patients (35%) who underwent liver biopsy, and in all but one of them did so by two or more stages. Janssens et al. ,117 therefore, suggested that more appropriate thresholds for the identification of severe (F3–F4) fibrosis in ALD would lie between 15.8 and 17.3 kPa. They did not report the sensitivity and the specificity of a threshold score of 12.5 kPa for identifying cirrhosis (F4) in patients with ALD, but suggested that a more appropriate threshold would lie between 19.6 and 23.5 kPa, the exact choice depending on the preferred balance between sensitivity and specificity. 117 This study was not ideally designed to establish specificity because biopsy was offered only to patients with a FibroScan score of ≥ 9.5 kPa.

Three studies discussed discordant results. 97,117,128 Nahon et al. 128 found that, relative to biopsy, FibroScan underestimated and overestimated the degree of fibrosis in approximately equal proportions of patients. Fourteen per cent (11/79) of those with histologically proven cirrhosis had FibroScan scores < 22.6 kPa, whereas 16% (11/68) of those with FibroScan scores > 22.6 kPa had biopsy results that did not indicate cirrhosis, although the majority (10/11) displayed extensive fibrosis. Janssens et al. 117 found that FibroScan overestimated the degree of fibrosis in 7 of the 11 patients with severe steatosis (by two stages in five patients and by one stage in two patients). Of the six patients in the study with alcoholic hepatitis, FibroScan classified three as having cirrhosis, although their biopsy results indicated F3 fibrosis. In two of the remaining three, both FibroScan and biopsy results indicated cirrhosis, thus removing the potential for overestimation by FibroScan. Finally, Lemoine et al. 97 noted one discordant case in a 70-year-old patient who had been totally abstinent from alcohol for 12 months and had no histological indication of alcoholic hepatitis. The patient’s FibroScan score was 38.10 ± 10 kPa, suggestive of PHt, although his HVPG measurement was only 8 mmHg.

Like Janssens et al. ,117 Mueller et al. 118 found that in patients with inflammatory hepatitis, liver stiffness was increased independently of the degree of fibrosis. They, therefore, found that the diagnostic accuracy of FibroScan improved when patients with laboratory signs of alcoholic steatohepatitis [i.e. serum glutamic oxaloacetic transaminase (SGOT) levels above 100 units/litre (U/L)] were excluded. When patients with only mildly elevated SGOT (> 50 U/L) were excluded, diagnostic accuracy improved in relation to F3–F4 fibrosis, but not in relation to F4 (cirrhosis) (Table 21).

Three small studies97,117,129 suggest that FibroScan can generally distinguish between patients with and without PHt, whereas one smallish study130 suggests that it can distinguish with less success between patients with and without large oesophageal varices (see Table 19).

There are no long-term data relating FibroScan results to survival or other clinical outcomes.

The Enhanced Liver Fibrosis Test and FibroTest: failure rates and adverse events

Both the ELF test and FibroTest use blood samples obtained by standard venepuncture. None of the included studies reported adverse events relating to this process. However, a systematic review of studies of adverse events in adults undergoing simple venepuncture for diagnostic or screening purposes indicates that between 14% and 45% of patients undergoing such venepuncture suffer pain and bruising, whereas between 0.9% and 3.4% suffer vasovagal reactions. Potentially disabling nerve injuries occur but, fortunately, appear to be very rare (for full details, see Appendix 8).

There are no data relating to test failure rates for the ELF test or FibroTest specifically in patients with ALD. The only relevant data come from Naveau et al. ’s study123 of FibroTest in which, for unspecified reasons, serum samples were unavailable for 17% (50/292) of the enrolled patients. In Rosenberg et al. ’s study121 of the ELF test, 4.4% (45/1021) of patients overall had incomplete clinical details or biochemical samples, compared with 5.6% (55/976) whose biopsy samples were considered inadequate; figures relating specifically to patients with ALD were not presented.

FibroScan: failure rates and adverse events

Only two of the included studies commented on the acceptability of FibroScan to patients. 117,132 Janssens et al. 117 found that only 2% (5/255) of patients entering hospital for alcohol detoxification and rehabilitation refused FibroScan, whereas 29% (21/72) of those with FibroScan results indicative of severe fibrosis or cirrhosis-refused liver biopsy. However, Nguyen-Khac et al. 132 found that 34% (55/160) of patients refused to participate in their study, which involved both transient elastography and venepuncture; it is not clear whether this reluctance to participate related specifically to one or other of those interventions, or to the perceived inconvenience of undergoing both.

Some studies reported the proportion of patients with ALD in whom FibroScan was unsuccessful: this ranged between 4.4% and 8.6% (Table 22). Other studies reported the number of potential participants who were excluded because of either failure to obtain a valid result or the presence of obesity or other factors likely to affect FibroScan performance. In the study by Kim et al. ,127 11.8% of patients were excluded because of the factors likely to affect test performance. Although obesity is the most frequently reported reason for FibroScan failure, Bureau et al. 129 found that one-third of test failures (2/6) in patients with liver disease of varied aetiology could not be attributed to obesity; their cause remained unclear.

Two studies that sought specifically to identify the features associated with successful FibroScan use did not meet the review’s inclusion criteria, but nonetheless provide useful information in this context. 79,139 The largest prospective study of this nature, by Castéra et al. ,79 assessed 13,369 examinations performed by seven operators over a 5-year period in 7261 adult patients with chronic liver disease of varied aetiology. It recorded the prevalence of failure of LSM (defined, in accordance with the manufacturer’s recommendation, as failure to obtain any value after at least 10 shots) and unreliable results (defined, again in accordance with the manufacturer’s recommendations, as < 10 successful shots, a success rate < 60%, or an interquartile range > 30% of the median value). In 18.4% of examinations (2466/13,369), valid results could not be obtained. LSM failed in 3.1% (420/13,369), whereas in 15.8% (2046/12,949) of the remaining examinations the results were deemed unreliable. Although the number of patients in whom FibroScan could be used successfully could be increased with repeated examinations, there remained some for whom it was impossible to obtain either any result or a reliable result after five attempts (Table 23). 79

Castéra et al. 79 found that the factor most strongly associated with both test failure and unreliable results at the first FibroScan examination was a BMI > 30 kg/m² (Table 24); the rates of both failure and unreliable results increased in parallel with the BMI (Table 25). The rates of both failure and unreliable results were also substantially raised when the operator had performed < 500 examinations (Table 26). Such a high threshold was chosen to define operator experience because all the operators who participated in the study had already performed at least 100 FibroScan examinations. The failure rate ranged from 0.2% in lean young non-diabetic patients to 20.9% in elderly obese diabetic patients, while the rate of unreliable results ranged from 7.2% in lean young men without diabetes or hypertension to 60.4% in elderly obese women with diabetes and hypertension.

In a smaller study, Kettaneh et al. 139 failed to achieve the manufacturer’s recommendation of at least 10 successful LSMs in 8.4% (79/935) of patients with chronic hepatitis C. They found that success was directly related to increased operator experience, and inversely related to both patient age and patient BMI. However, with hindsight, they suggested that the limiting factor was not so much BMI per se as the presence of a fatty thoracic belt that made it technically impossible to obtain accurate results.

A pilot study conducted specifically in patients with a BMI of ≥ 30 kg/m² found that the use of the XL specialised probe, which can measure to a depth of 35–75 mm below the skin surface, reduced rates of failure and unreliable results. However, even with this probe, no value could be obtained in 12% of patients and the recommended standard of at least 10 valid measurements could be achieved in only 76%. 140 These findings are particularly important in the light of the high proportion of the UK population with a BMI of ≥ 30 kg/m² or a raised waist circumference (see Chapter 1, Incidence and prevalence).

Diagnostic and prognostic accuracy

Patient management and clinical outcomes

No studies were identified that reported data relating to the effect of the use of any of the four tests on patient management or clinical outcomes.

Adverse effects and contraindications

The non-invasive tests included in this review appear to be safe. No adverse effects were reported in any of the included studies and no additional evidence has been identified that indicates that transient elastography is specifically associated with any adverse effects. As noted in The Enhanced Liver Fibrosis Test and FibroTest: failure rates and adverse events, the ELF test, FibroTest, and FibroMAX, which utilise blood tests, will be associated with the same adverse effects as diagnostic venepuncture generally – primarily pain and bruising, with occasional vasovagal reactions, and very rarely potentially disabling nerve injuries. By contrast, liver biopsy is associated with a high level of morbidity and occasional mortality (see Chapter 1, Liver biopsy).

No contraindications have been specified for the ELF test. The contraindications specified for FibroTest, FibroMAX, and FibroScan all relate to the mode of operation of the test, and do not relate to any potential for harm in patients with the relevant characteristics. Moreover, there is evidence to suggest that FibroScan is generally acceptable to patients with ALD. As noted in FibroScan: failure rates and adverse events, Janssens et al. 117 found that only 2% of patients entering hospital for alcohol detoxification and rehabilitation refused FibroScan, although 34% refused to participate in the study by Nguyen-Khac et al. 132 which required them to undergo both FibroScan and blood tests. Finally, in a study of acceptability, Melin et al. 145 found that all 380 patients seen for alcohol problems during the course of a year agreed to undergo FibroScan; only 5% (2/44) of those who were offered liver biopsy because their FibroScan result indicated severe fibrosis or cirrhosis refused it, compared with 29% in the study by Janssens et al. 117

Internal and external validity

The results of the included studies summarised above suggest that the ELF test, FibroTest, and FibroScan can be used to identify patients with ALD who have fibrosis or cirrhosis. However, these results should be viewed with caution for a number of reasons. The most obvious reason is that they are not robust because they rest on data from relatively few patients with ALD; this is especially true of the ELF test.

Population

• Adults.

Intervention

• Percutaneous or transjugular liver biopsy.

Outcomes

• Adverse events probably or possibly caused by the liver biopsy.

Setting

• Any country.

Study type

• Any study design which presented data relating to over 100 patients.

Population

• Fewer than 100 participants (either overall or in either arm of a RCT comparing percutaneous with transjugular biopsy).

Intervention

• Laparoscopic liver biopsy.

• Biopsy undertaken prior to 1980.

Study type

• Animal models.

• Narrative reviews, editorials, opinions.

FIGURE 28.

Adverse effects of liver biopsy: summary of study selection and exclusion.