Transient elastography for diagnosis of hepatic fibrosis in people with alcoholic liver disease

  • Protocol
  • Diagnostic

Authors

  • Chavdar S Pavlov,

    Corresponding author
    1. Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, The Cochrane Hepato-Biliary Group, Copenhagen, Denmark
    2. I.M. Sechenov First Moscow State Medical University, Clinic of Internal Diseases Propedeutics, Moscow, Russian Federation
    • Chavdar S Pavlov, The Cochrane Hepato-Biliary Group, Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, Blegdamsvej 9, Copenhagen, DK-2100, Denmark. chpavlov@mail.ru.

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  • Giovanni Casazza,

    1. University of Milan, Dipartimento di Scienze Biomediche e Cliniche "L. Sacco", Milan, Italy
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  • Dimitrinka Nikolova,

    1. Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, The Cochrane Hepato-Biliary Group, Copenhagen, Denmark
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  • Vladimir T Ivashkin,

    1. I.M. Sechenov First Moscow State Medical University, Clinic of Internal Diseases Propedeutics, Moscow, Russian Federation
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  • Christian Gluud

    1. Copenhagen Trial Unit, Centre for Clinical Intervention Research, Department 7812, Rigshospitalet, Copenhagen University Hospital, The Cochrane Hepato-Biliary Group, Copenhagen, Denmark
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Abstract

This is a protocol for a Cochrane Review (Diagnostic test accuracy). The objectives are as follows:

To determine the diagnostic accuracy of transient elastography for detecting hepatic fibrosis in people with alcoholic liver disease when compared with liver biopsy as reference standard. In particular, no significant hepatic fibrosis (F0, F1) and significant hepatic fibrosis (F2, F3, F4), no cirrhosis (F0, F1, F2, F3) and cirrhosis (F4).

Background

Transient elastography is a widely used non-invasive method for assessment of hepatic fibrosis (scarring of the liver tissue), leading to stiffening of the liver. Transient elastography investigation for liver fibrosis by measuring the liver stiffness has already been validated in many people with chronic liver diseases (Sandrin 2003; Nahon 2008). An important aspect of liver stiffness measurements are cut-off values that characterise different stages of fibrosis. However, the cut-off levels for the stages of fibrosis are different in the different chronic liver diseases, but what is more, the cut-off levels for people with alcoholic liver disease are not established yet (Rockey 2008). The presence and progression of hepatic fibrosis into cirrhosis is a main prognostic variable having impact on survival in people with alcoholic liver disease. Transient elastography may indicate the amount of hepatic fibrosis in people with alcoholic liver disease (de Lédinghen 2010). A number of clinical studies have compared liver stiffness measured by transient elastography with presence of hepatic fibrosis detected on liver biopsy, reaching a conclusion that transient elastography is a reliable method for assessment of hepatic fibrosis (Foucher 2006; Gómez-Domínguez 2006; Ivashkin 2011a; Tsochatzis 2011). In addition, studies have found a correlation between the level of liver stiffness and the degree of hepatic fibrosis in people with alcoholic liver disease (Nguyen-Khac 2008; Nahon 2009; Mueller 2010). The prevalence of hepatic fibrosis in heavy drinkers is not well known. In a series of 1407 people with alcoholic liver disease diagnosed on liver biopsy, 809 (57.5%) people had developed liver fibrosis (Naveau 1997). This is why the correct staging of liver stiffness is of paramount importance for the treatment strategy of people with liver injuries (O'Shea 2010).

Target condition being diagnosed

Hepatic fibrosis in people with alcoholic liver disease

All people with alcoholic liver disease are at risk of developing liver fibrosis. This risk is especially higher in people who are binge drinkers, people with increased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, or in people with severe steatohepatitis on liver biopsy (Bouchier 1992).

Hepatic fibrosis may develop due to weekly alcohol consumption of seven to 13 beverages for women (one beverage = 12 g alcohol) and 14 to 27 beverages for men in the course of five or more years (Savolainen 1993; Becker 1996). The risk ratio of progression of fibrosis to cirrhosis increases significantly with a daily consumption of 20 to 40 g ethanol in women and more than 80 g ethanol in men (Sherlock 1997; O'Shea 2010). Fatty liver, the most common lesion that develops due to excessive ethanol intake, is potentially reversible through abstinence, but the amount of fat in the liver is an important predictor of the risk of subsequent cirrhosis in those who continue to drink (Sørensen 1984).

The liver is the main site of alcohol metabolism acting through two hepatic enzymes, alcohol dehydrogenase and cytochrome P-450 (CYP) 2E1. Increased alcohol intake disrupts the metabolic liver function, and, as a result, alcoholic liver disease develops (Stewart 2001). Histologically, alcoholic liver disease occurs in three forms: fatty liver or steatosis, alcoholic hepatitis, and chronic hepatitis with hepatic fibrosis and cirrhosis (O'Shea 2010). Morphological features that predict progression to hepatic fibrosis and cirrhosis include severe steatosis, giant mitochondria, and the presence of mixed macrovesicular-microvesicular steatosis (Teli 1995).

Timely staging of hepatic fibrosis in people with alcoholic liver diseases could motivate patients and physicians in finding an optimal strategy for treatment of the disease. A single staging system for evaluating hepatic fibrosis in alcoholic liver disease does not exist. METAVIR is the most widely used scoring system for interpretation of liver biopsy results based on the stage of fibrosis where F0 indicates no fibrosis, F1 - portal fibrous expansion, F2 - thin fibrous septa emanating from portal triads, F3 - fibrous septa bridging portal triads and central veins, and F4 indicates cirrhosis (Table 1). Hepatic fibrosis could be considered clinically significant if defined as F2 or greater than F2, using METAVIR score (Franciscus 2007). In Table 1 we have also included other widely used systems for classification of fibrosis in people with alcoholic liver disease (Knodell 1981; Desmet 1994; Ishak 1995; Brunt 1999; Kleiner 2005).

Table 1. Semi-quantitative histopathological scoring systems for progression of fibrosis to cirrhosis. Conversion grid for the stages of hepatic fibrosis*
  1. F = stage of hepatic fibrosis.
    F0 - no fibrosis; F1 - portal fibrous expansion; F2 - thin fibrous septa emanating from portal triads; F3 - fibrous septa bridging portal triads and central veins; F4 - cirrhosis. Clinically significant fibrosis is generally defined as F2 or greater (on the METAVIR scale from F0 to F4 with F4 being cirrhosis).

    METAVIR, Knodell, Ishak, Kleiner, Desmet, and Brunt scoring systems are used to classify fibrosis (and steatosis) due to alcoholic liver disease. For references, please see text.

    *Adapted from Goodman 2007.

METAVIR

Stage of
estimated fibrosis

Knodell

Stage of
estimated fibrosis

Ishak

Stage of
estimated fibrosis

Kleiner

Stage of
estimated fibrosis

Desmet

Stage of
estimated fibrosis

Brunt

Stage of
estimated fibrosis

F0F0F0F0F0F0
F1F1F1F1F1F1
F1F1F2F1F1F1
F2F3F3F2F2F2
F3F3F4F2F3F3
F4F4F5F3F4F4
F4F4F6F4F4F4

Index test(s)

Transient elastography is designed to measure liver stiffness, using FibroScan® equipment (Echosens, Paris, France; Echosens 2009). A probe, consisting of an ultrasound transducer located at the end of a vibrating piston, is put on the skin surface overlying the liver (the person is in supine position). After pressing the button on the probe, a pulse wave is transmitted across the liver parenchyma. After a short interval, a second, ultrasound wave is transmitted. The difference between the velocities of the two waves in the liver parenchyma is calculated using the Doppler technique (Sandrin 2003; Nahon 2008). As it is known from physical principles, the velocity of the pulse wave increases with the stiffness of the liver parenchyma, corresponding to increasing severity of fibrosis.

Liver stiffness is expressed as a median value of 10 measurements in kiloPascals (kPa). The findings of 'normal' liver stiffness values for apparently healthy women and men differ in different studies, lying between 3.3 kPa and 7.0 kPa, using the 5th and 95th percentiles (Roulot 2008; Kim 2012). While age is not found to affect liver stiffness, men compared to women have slightly higher liver stiffness values (Roulot 2008). A predefined cut-off of 8.00 kPa is predictive of severe hepatic fibrosis in alcoholic liver disease, equal or greater than F3 by the METAVIR scoring system (Mueller 2010). The transient elastography method is non-invasive, simple, highly reproducible, and allows examination of at least 100 times larger volume of liver tissue compared to a liver sample obtained through liver biopsy (de Lédinghen 2008). This is why the sampling error of transient elastography investigation is less than with liver biopsy (Ingiliz 2009). Other advantages of transient elastography are that it has a higher performance in detecting cirrhosis and has likely higher prognostic value in cirrhosis. Transient elastography increases its diagnostic accuracy when applied in combination with serum markers (Castera 2010). The diagnostic accuracy of transient elastography was compared with alternative tests such as acoustic radiation forced impulse (ARFI) imaging and a serum marker, enhanced liver fibrosis (ELF), concluding that transient elastography can be used for diagnosis of liver fibrosis alone or in combination with any of them (Crespo 2012). Janssens et al have shown that transient elastography is more accurate than other currently available serum markers for people with chronic hepatitis C (Janssens 2010). However, the diagnostic accuracy of transient elastography in people with alcoholic liver disease is not established yet.

Alternative test(s)

Different methods to perform elasticity measurements have been developed since 1990. They are aimed at quantifying the elasticity or viscoelasticity of the liver tissue. There are two common elements in every elasticity imaging method: a force or stress is applied on the liver tissue and the obtained mechanical response is measured.

Siemens Ltd. (i.e. ACUSON S2000) is a medical technology that can detect hepatic fibrosis, and hence, it enables the quantification of the hepatic fibrosis in its different stages. The technology is also called liver elastography, performed using ARFI imaging (Iyo 2009). ARFI imaging is faster than conventional methods as ARFI uses higher frequencies that are comparable to those used in colour Doppler imaging. The images have greater contrast and the boundary of the focal lesions are better defined compared with the conventional ultrasonography imagining techniques (Iyo 2009).

Ultrasonography measures the progression, stagnation, or regression of hepatic fibrosis in alcoholic liver disease (Caballeria 1998). It allows investigation of the hepatic tissue through generation of ultrasonic waves. Different ultrasonography impedance indices based on Echo-colour Doppler variables of the liver blood flow have been proposed for indirect estimation of the stage of hepatic fibrosis (Ersoz 1999; Hizli 2010; Ivashkin 2011a). We are undertaking a systematic review to assess the diagnostic accuracy of ultrasonography for diagnosis of hepatic fibrosis and cirrhosis in people with alcoholic liver disease (Pavlov 2013a).

Supersonic shear imaging (SSI) is a technique that investigates tissue elasticity to detect hepatic fibrosis and steatosis. It is based on velocity estimation of a shear wave, generated by a radiation force (Bercoff 2004).

Magnetic resonance elastography (MRE) combines magnetic resonance imaging (MRI) with sound waves to create a visual map (elastogram), showing the stiffness of the liver tissue. It is used primarily to detect hardening of the liver caused by different types of liver diseases, including those of alcoholic aetiology (Jin 2007).

Other alternative non-invasive tests (apart from venepuncture) to transient elastography are laboratory tests such as ALT and AST ratio, prothrombin index, hyaluronic acid, ELF, etc. (Crespo 2012; Liu 2012). All of these tests are used as surrogate markers for estimation of hepatic fibrosis. In addition, different combinations of biochemical tests such as FibroTest® and Fibrometre® are used for diagnosis of hepatic fibrosis in people with alcoholic liver disease (Morra 2007; Poynard 2007; Poynard 2008; Angulo 2009). We are also undertaking a systematic review to determine the diagnostic accuracy of transient elastography plus FibroTest® versus FibroTest® alone for diagnosis of hepatic fibrosis in adults with chronic hepatitis C (Pavlov 2013b).

Clinical pathway

The clinical pathway in diagnosis of alcoholic liver disease is presented in Figure 1.

Figure 1.

Clinical pathway in the diagnosis of alcoholic liver disease.

Rationale

Liver biopsy has so far been considered the standard method for detection of hepatic fibrosis and its staging, using different semi-quantitative morphological scores on liver tissue samples with a size of no more than 1 to 2 cm3 (Table 1). One advantage of liver biopsy is that it may give diagnostic information for concurrent liver diseases (Poulsen 1979; Ismail 2011). However, there are a number of disadvantages with liver biopsy; it is invasive, and it may hide potential risks to the person such as punctures of abdominal organs and haemorrhage. Liver biopsy can be painful, time-consuming, and stressful for the person and depends on the physician's experience and skills (Grant 1999; O'Shea 2010; Ivashkin 2011b). The risk of haemorrhage and death after liver biopsy is especially higher in people with a platelet count of 60,000 per mm3 or less, and also in those with an international normalisation ratio greater than 1.3 (Seeff 2010). The small size of the tissue samples may also lead to sampling errors.

Consensus on using transient elastography as a non-invasive method for diagnosis of hepatic fibrosis has not been established (Rockey 2008). It is still under debate if confounding factors such as inflammation, cholestasis, and increased hepatic vein congestion, such as in chronic heart failure, influence the precision of transient elastography in people with alcoholic liver disease (Rockey 2008). Increased body mass index, sex, and age are not considered confounding factors, but they may affect the number of reliable results (i.e. success rate).

Published meta-analyses demonstrated that cause is the most important factor leading to heterogeneity, thus indicating that the different chronic liver diseases should be analysed separately (Friedrich-Rust 2008; Poynard 2008; Stebbing 2010; Tsochatzis 2011). However, in these meta-analyses, results are obtained for all causes of liver disease together, which may become a limitation for determining the diagnostic accuracy of the method of transient elastography when used to diagnose hepatic fibrosis in people with alcoholic liver disease. Furthermore, these meta-analyses do not examine in detail the possible confounding influences of factors such as the degree of hepatic steatosis or the level of liver inflammation activity in people with alcoholic liver disease (Sackett 2002). This review aims to complete present research and to study further the diagnostic accuracy of transient elastography in detecting the presence or absence of hepatic fibrosis in people with alcoholic liver disease, following the Cochrane methodology (SRDTA Handbook). In addition, this review will help researchers working on designing interventions for people with alcoholic liver disease by knowing the grade and progression of fibrosis and cirrhosis.

Objectives

To determine the diagnostic accuracy of transient elastography for detecting hepatic fibrosis in people with alcoholic liver disease when compared with liver biopsy as reference standard. In particular, no significant hepatic fibrosis (F0, F1) and significant hepatic fibrosis (F2, F3, F4), no cirrhosis (F0, F1, F2, F3) and cirrhosis (F4).

Methods

Criteria for considering studies for this review

Types of studies

We will include diagnostic cohort studies and diagnostic case-control studies designs that have assessed hepatic fibrosis in participants with alcoholic liver disease through transient elastography and liver biopsy, irrespective of language or publication status, or whether data were collected prospectively or retrospectively.

Participants

The studies will have included participants of any sex and ethnic origin, above 16 years old, and who were diagnosed with alcoholic liver disease. The participants could have been hospitalised or outpatients. The diagnosis of alcoholic liver disease will have been established in the study participants based on registered history of alcohol excessive intake of sufficient duration and quantity together with clinical evidence of liver disease expressed with physical signs at examination and followed by laboratory evidence of liver disease. Other causes of liver disease, such as hepatitis, autoimmunity, metabolic diseases, and toxins, will thus be excluded. To ascertain the diagnosis of alcoholic liver disease and study the presence or absence of liver fibrosis or cirrhosis, or both, both transient elastography and liver biopsy should have been performed.

Bouchier 1992

We will exclude people with other causes of liver injury, such as non-alcoholic fatty liver disease, chronic hepatitis C virus infection, chronic hepatitis B virus infection, autoimmune liver disease, or human immunodeficiency virus (HIV)-infection.

Index tests

Transient elastography, a non-invasive test measuring liver stiffness in kiloPascals (kPa).

Following the recommended technical parameters for transient elastography and to ensure the validity of the transient elastography result for every participant in the single studies, participants should have undergone at least 10 validated stiffness measurements at the same measurement point. The measurements should have an interquartile range of 30% or less, and the ratio of the number of successful measurements to the total number of acquisitions should be 60% or less (Echosens 2009). We will only consider data from people who provide the full set of data as described here.

Transient elastography is not recommended for use in pregnant women, people with pacemakers, and people with ascites.

Target conditions

The target condition is presence or absence of hepatic fibrosis (i.e. no significant hepatic fibrosis (F0, F1) and significant hepatic fibrosis (F2, F3, F4)) or cirrhosis (i.e. no cirrhosis (F0, F1, F2, F3) and cirrhosis (F4)) in people with alcoholic liver disease.

Reference standards

Liver biopsy is the reference standard that is obtained by percutaneous needle techniques, transjugular method, ultrasound-guided fine-needle, or surgical specimens (Kuntz 2008; Ivashkin 2011b).

Liver biopsy is the only existing reference standard so far for diagnosing different grades of fibrosis in people with alcoholic liver disease.

If liver biopsy samples are reported with any of the semi-quantitative scores, that is, METAVIR (Franciscus 2007), Knodell (Franciscus 2007), Ishak (Franciscus 2007), Kleiner (Kleiner 2005), Scheuer (Regev 2002), or Brunt (Brunt 1999), we will use a conversion grid for hepatic fibrosis staging adapted after Goodman 2007 (Table 1) to unify results on the grade of hepatic fibrosis on liver biopsy. For grading steatosis, we will use the Nonalcoholic Steatohepatitis Clinical Research Network scoring system (Kleiner 2005) (Table 2). Other semi-quantitative histopathological scoring systems would be added if such were used in the included studies.

Table 2. Nonalcoholic Steatohepatitis Clinical Research Network scoring system for grade of hepatic steatosis
Evaluation of parenchymal involvement by steatosisSteatosis grade
less than 5%0
5% to 33%1
34% to 66%2
more than 66%3

Search methods for identification of studies

We will combine electronic searches with reading references of identified studies of possible interest.

Electronic searches

We will search The Cochrane Hepato-Biliary Group Diagnostic Test Accuracy Studies Register (hbg.cochrane.org/specialised-register), and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (Wiley), MEDLINE (PubMed), EMBASE (Ovid SP), and the Science Citation Index Expanded (de Vet 2008).

We will also screen references of the retrieved studies to identify other potentially relevant studies for inclusion in our review.

The preliminary search strategies for the different databases with the time span for the searches are given in Appendix 1. The given search strategies may be improved at the review preparation phase.

Searching other resources

Abstracts, published in conference proceedings or presented as posters, will be eligible for inclusion if retrieved with the search results or if found in the reference lists of the studies of interest to this review.

Data collection and analysis

We will follow the guidelines provided in the draft Cochrane Diagnostic Reviewer's Handbook (Reitsma 2005; de Vet 2008).

Selection of studies

Two review authors, independently of each other, will identify studies for possible inclusion in the review by reading abstracts of the search results. We will exclude the references with a study design not fulfilling the inclusion criteria of our review protocol.

We will retrieve publications in full to do a second selection of relevant studies. If we identify multiple publications on a study fulfilling the inclusion criteria of our review protocol, then these publications will be screened for data not provided in the already identified publications.

The studies that we include must evaluate transient elastography in the diagnosis of hepatic fibrosis severity using liver biopsy as the reference standard.

The maximum time interval of investigation with liver biopsy and transient elastography will not exceed three months.

Data extraction and management

Two review authors, independently of each other, will extract data, using a data extraction sheet. The data needed for the conductance of this systematic review are study origin, year and language of publication, study design, participants' epidemiological and laboratory characteristics, the definition of alcoholic liver disease as defined by the authors of the individual studies considered for inclusion, technical failures in undertaking liver biopsy and transient elastography, cut-offs of liver stiffness, grade of hepatic fibrosis estimated by morphological score, and information related to the QUADAS-2 items for evaluation of the bias risk of the studies (Whiting 2011).

A third review author will act as arbitrator in case of disagreements between the review authors extracting the information.

In order to provide data for our analyses, the studies must provide data that can help us calculate the true positive (TP), false positive (FP), true negative (TN), and false negative (FN) diagnostic values of the reference standard, liver biopsy, as well as the index test, transient elastography, for diagnosing the stages of fibrosis, based on semi-quantitative morphological scores and cut-off points for liver stiffness, respectively, and as described by the authors of the identified studies.

If information on any of the TP, FP, FN, and TN diagnostic test values or results are missing, we will attempt to contact the authors of the included studies for this and other missing information. If no reply is received, we will still list the study under 'Included studies', but we will not use it for statistical analyses. However, we may still be able to assess the degree of outcome reporting bias.

Assessment of methodological quality

Design flaws in test accuracy studies can produce biased results (Lijmer 1999; Whiting 2004; Rutjes 2006). In addition, evaluation of study results is quite often impossible due to incomplete reporting (Smidt 2005).

To limit the influence of different biases, two review authors, independent of each other, will assess the bias risk of the included diagnostic test accuracy studies, using QUADAS-2 domains (Whiting 2011). A third review author will act as arbitrator in case of disagreements between the authors assessing the bias risk of the studies. We will attempt to contact the authors of studies if information on methodology is lacking, in order to assess correctly the bias risk of the studies.

The presented items in Appendix 2 are adopted to serve the purposes of our review in addressing the patient spectrum, index test, target condition and reference standard, and flow and timing, and which answers would also reflect the general quality of the included studies.

QUADAS-2 is not used to generate a summary 'quality score', because of the well-known problems associated with such scores (Juni 1999; Whiting 2005). If a study is judged as 'low' on all domains relating to bias or applicability, then it is appropriate to have an overall judgement of 'low risk of bias' or 'low concern regarding applicability' for that study. If a study is judged 'high' or "'unclear' on one or more domains, then it may be judged 'at risk of bias' or as having 'concerns regarding applicability'. Any differences in the methodological quality assessment will be resolved by a third review author.

We will use tabular and graphical displays to summarise QUADAS-2 assessments.

Statistical analysis and data synthesis

We will carry out the analyses following Chapter 10: Analysing and Presenting Results as recommended in the Cochrane Handbook for Systematic Reviews of Diagnostic Test Accuracy (Macaskill 2008). We will use the Review Manager 5 software for analyses and plots (RevMan 2011).

We will build two-by-two tables of the transient elastography performance (TP, TN, FP, FN) for each primary study and for all of the predefined stages of the disease (i.e. significant fibrosis, cirrhosis, etc.). We will estimate sensitivity, specificity, positive and negative likelihood ratios (LR+ and LR-), positive and negative predictive values (PPV and NPV) with their 95% confidence intervals (CI). First, we will perform a graphical descriptive analysis of included studies: forest plots (sensitivity and specificity separately) and we will provide a graphical representation of the studies in the receiver operating characteristic (ROC) space (sensitivity and 1-specificity, with their 95% CIs). Second, where appropriate, we will perform a meta-analysis. Since we expect that the primary studies will report accuracy estimates of transient elastography using different cut-off points, we will use the hierarchical summary ROC model (HSROC) (Rutter 2001) to pool data (sensitivities and specificities) and to plot a summary ROC curve.

The estimates obtained from the fitted models will be used to calculate summary estimates of LRs.

For primary studies that report accuracy results for more than one cut-off point, we will report sensitivities and specificities for all the cut-off points, but we will use a single cut-off point for each study in HSROC (or bivariate model) analysis. We will base the choice of the cut-off on the maximum of the Youden's index (sensitivity + specificity - 1). We are aware that this method for the selection of the cut-off point may lead to an overestimate of diagnostic accuracy (Leeflang 2008). However, there are no accepted thresholds to a priori define a positive liver stiffness measurement, and, also, the studies that report accuracy estimates for only one cut-off have probably based the selection of the reported cut-off on the same criterion (Youden's index).

Finally, if possible, we will add some relevant co-variates (see sources of heterogeneity) to the model to investigate the effect of the predefined sources of heterogeneity.

We will perform all of the statistical analyses with a statistical software, SAS, release 9.2.

Investigations of heterogeneity

We will investigate the sources of heterogeneity by evaluating differences of diagnostic accuracy in predefined subgroups, and related to:

  1. liver biopsy as the reference standard:

    1. different levels of inflammation according to the liver biopsy (below two grades compared to two or greater grades of activity);

    2. different lengths of liver biopsy sample (less than 15 mm compared to 15 mm or more than 15 mm);

    3. different number of portal tracts included in a liver biopsy sample (less than seven compared to seven or more than seven);

    4. different grades of steatosis according to the liver biopsy (less than 5% compared to 5% or more than 5%);

    5. mild fibrosis compared to intermediate fibrosis compared to advanced fibrosis as estimated by the different semi-quantitative histopathological scoring systems used (see Table 1);

  2. population group:

    1. different body mass indices (BMI) (below 25 kg/m2 compared to 25 kg/m2 or more than 25 kg/m2) (BMI);

    2. serum levels of AST activity (normal compared to greater than the upper limit (Dufour 2000));

  3. study design (diagnostic cohort study designs compared to case-control study designs);

  4. definition of alcoholic liver disease.

The effect of the above-mentioned sources of heterogeneity on the accuracy estimates will be evaluated by adding co-variates to the bivariate or HSROC model.

Sensitivity analyses

To assess the effect of risk of bias of the included studies on the diagnostic accuracy, a sensitivity analysis will be performed by excluding studies at high risk of bias. A study will be classified at high risk of bias if judged as high risk of bias in at least one of the domains of QUADAS-2 (Appendix 2).

Assessment of reporting bias

We will perform a funnel plot for investigating reporting bias. We will assess bias by visually assessing the funnel plot. The statistical methods suggested by Deeks et al will also be used to investigate funnel plot asymmetry (Deeks 2005).

Acknowledgements

We would like to thank:

  • The editors from The Diagnostic Accuracy Reviews Editorial Team.

  • Sarah Louise Klingenberg, Denmark, for drafting preliminary search strategies, and Mirella Fraquelli, Italy, and Agostino Colli, Italy, for many useful comments during the preparation of this protocol.

  • Peer reviewers: Juan Christobal Gana, Peru; Yun Xia, China; Mona H. Ismail, Saudi Arabia.

  • Contact Editors from The CHBG: Mirella Fraquelli, Italy; Agostino Colli, Italy.

Appendices

Appendix 1. Search Strategy

DatabaseTime spanSearch strategy
Cochrane Hepato-Biliary Group Controlled Trials RegisterDate will be given at review stage('transient elastograph*' OR fibroscan) AND ((hepatic OR liver) AND (fibrosis OR cirrhosis))
Cochrane Hepato-Biliary Group Diagnostic Test Accuracy RegisterDate will be given at review stage('transient elastograph*' OR fibroscan) AND ((hepatic OR liver) AND (fibrosis OR cirrhosis))
The Cochrane LibraryDate will be given at review stage

#1 MeSH descriptor: [Elasticity Imaging Techniques] explode all trees

#2 transient elastograph* or fibroscan

#3 #1 or #2

#4 MeSH descriptor: [Liver Cirrhosis] explode all trees

#5 (hepatic or liver) and (fibrosis or cirrhosis)

#6 #4 or #5

#7 #3 and #6

MEDLINE (Ovid SP)1946 to the date of search

1. exp Elasticity Imaging Techniques/

2. (transient elastograph* or fibroscan).mp. [mp=title, abstract, original title, name of substance word, subject heading word, protocol supplementary concept, rare disease supplementary concept, unique identifier]

3. 1 or 2

4. exp Liver Cirrhosis/

5. ((hepatic or liver) and (fibrosis or cirrhosis)).mp. [mp=title, abstract, original title, name of substance word, subject heading word, protocol supplementary concept, rare disease supplementary concept, unique identifier]

6. 4 or 5

7. 3 and 6

EMBASE (Ovid SP)(1974 to the date of search)

1. exp elastography/

2. (transient elastograph* or fibroscan).mp. [mp=title, abstract, subject headings, heading word, drug trade name, original title, device manufacturer, drug manufacturer, device trade name, keyword]

3. 1 or 2

4. exp liver cirrhosis/

5. ((hepatic or liver) and (fibrosis or cirrhosis)).mp. [mp=title, abstract, subject headings, heading word, drug trade name, original title, device manufacturer, drug manufacturer, device trade name, keyword]

6. 4 or 5

7. exp biopsy/

8. liver biops*.mp. [mp=title, abstract, subject headings, heading word, drug trade name, original title, device manufacturer, drug manufacturer, device trade name, keyword]

9. 7 or 8

10. 3 and 6 and 9

Science Citation Index Expanded ( apps.webofknowledge.com ) 

#3 1,181 #2 AND #1

#2 66,256 TS=((hepatic or liver) and (fibrosis or cirrhosis))

#1 1,703 TS=(transient elastograph* or fibroscan)

 

Appendix 2. QUADAS-2

DOMAINPARTICIPANT SELECTION  INDEX TEST REFERENCE STANDARDFLOW AND TIMING 
Description

Describe methods of participant selection: describe included participants (prior testing, presentation, intended use of index test and setting): 

The studies that fulfil the inclusion criteria of this review should have included participants of any sex and ethnic origin, above 16 years old, and who were diagnosed with alcoholic liver disease. The participants could have been hospitalised or outpatients.

The diagnosis alcoholic liver disease should have been established in the study participants based on registered history of alcohol excessive intake of sufficient duration and quantity together with clinical evidence of liver disease expressed with physical signs at examination and followed by laboratory evidence of liver disease. To ascertain the diagnosis of alcoholic liver disease and study the presence or absence of liver fibrosis or cirrhosis or both in each of the study participants, both transient elastography and liver biopsy should have been performed.

Describe the index test and how it was conducted and interpreted: 

Transient elastography for grading hepatic fibrosis conducted either before or after liver biopsy.

The recommended technical parameters of transient elastography investigation are at least 10 validated stiffness measurements at the same measurement point, an interquartile range of no more than 30%, and the ratio of the number of successful measurements to the total investigational number of acquisitions should be no less than 60% (www.echosens.com/pdf/FS402_WEB.pdf).

Describe the reference standard and how it was conducted and interpreted: 

Liver biopsy is useful in establishing the grade of hepatic fibrosis in people with alcoholic liver disease.

The morphological interpretation of the liver biopsy samples is reported with semi-quantitative scores, such as METAVIR, Knodell, Ishak, Kleiner, Scheuer, or Brunt (see Table 1).

The Nonalcoholic Steatohepatitis Clinical Research Network scoring system is used for grading steatosis (Kleiner 2005) (Table 2).

Describe any people who did not receive the index test(s) or reference standard (or both) or who were excluded from the 2 x 2 table (refer to flow diagram): describe the time interval and any interventions between index test(s) and reference standard:

As fibrosis may develop rapidly within time, we will exclude participants if the time interval between diagnostic liver biopsy and transient elastography investigations is longer than three months, an arbitrary chosen time interval.

Signalling questions: yes/no/unclear

Was a consecutive or random sample of participants enrolled?

Yes: all consecutive participants or random sample of people with diagnosed alcoholic liver disease were enrolled in the study.

No: selected participants were not included.

Unclear: insufficient data were reported to permit a judgement.

Were the index test results interpreted without knowledge of the results of the reference standard?

Yes: transient elastography test results were interpreted without knowledge of the results of the liver biopsy.

No: transient elastography results were interpreted with knowledge of the results of the liver biopsy.

Unclear: insufficient data were reported to permit a judgement.

Is the reference standard likely to classify the target condition correctly?

Yes: if all participants have undergone liver biopsy and the morphological results were correctly reported.

No: if all participants have not undergone liver biopsy or morphological results were not correctly reported.

Unclear: insufficient data were reported to permit a judgement.

Was there an appropriate interval between index test(s) and reference standard?

Yes: the interval between the transient elastography and liver biopsy was less than or equals three months.

No: the interval between the transient elastography test and liver biopsy was more than three months.

Unclear: insufficient data were reported to permit a judgement.

Was a case-control design avoided?

Yes: case-control design was avoided.

No: case-control design was not avoided.

Unclear: insufficient information was reported to permit a judgement.

If a threshold was used, was it prespecified?

Yes: if the threshold for a positive test was prespecified.

No: if the threshold for a positive test was not prespecified.

Unclear: insufficient data were reported to permit a judgement.

Were the reference standard results interpreted without knowledge of the results of the index test?

Yes: liver biopsy results were interpreted without knowledge of the results of the transient elastography test.

No: liver biopsy results were interpreted with the knowledge of the results of the transient elastography test.

Unclear: insufficient data were reported to permit a judgement.

Did all participants receive the reference standard?

Yes: all participants underwent the reference standard, liver biopsy.

No: not all participants underwent liver biopsy.

Unclear: insufficient data were reported to permit a judgement.

Did the study avoid inappropriate exclusions?

Yes: the study avoided inappropriate exclusions (i.e. difficult to diagnose participants).

No: the study excluded patients inappropriately.

Unclear: insufficient data were reported to permit a judgement.

Did all participants receive the same reference standard?

Yes: all participants received the same reference standard, i.e. liver biopsy.

No: not all participants received the same reference standard, i.e. liver biopsy.

Unclear: insufficient data were reported to permit a judgement.

Were all participants included in the analysis?

Yes: all participants meeting the selection criteria (selected participants) were included in the analysis, or data on all the selected participants were available so that a 2 x 2 table including all selected participants could be constructed.

No: not all participants meeting the selection criteria were included in the analysis or the 2 x 2 table could not be constructed using data on all selected participants.

Unclear: insufficient data were reported to permit a judgement.

Risk of bias: high/low/unclear

Could the selection of participants have introduced bias?

High risk of bias: yes, if the selection of participants have introduced bias.

Low risk of bias: no, if the selection of participants have not introduced bias.

Unclear risk of bias: insufficient data on participants selection were reported to permit a judgement on the risk of bias.

Could the conduct or interpretation of the index test have introduced bias?  

High risk of bias: if the answer to the signalling questions on the conduct or interpretation of the index test is "no".

Low risk of bias: if the answer to the signalling questions on the conduct or interpretation of the index test is "yes".

Unclear risk of bias: if the answers to the two signalling questions on the conduct or interpretation of the index test is either "unclear" or any combination of "unclear" with "yes" or "no".

Could the reference standard, its conduct, or its interpretation have introduced bias?

High risk of bias: if the answer to the signalling questions on the reference standard, its conduct, or its interpretation is "no".

Low risk of bias: if the answer to the signalling questions on the reference standard, its conduct, or its interpretation is "yes".

Unclear risk of bias: if the answers to the three signalling questions on the reference standard, its conduct, or its interpretation is either "unclear" or any combination of "unclear" with "yes" or "no".

Could the participant flow have introduced bias?

High risk of bias: if the answer to the signalling questions on flow and timing is "no".

Low risk of bias: if the answer to the signalling questions on flow and timing is "yes".

Unclear risk of bias: if the answers to the 4 signalling questions on flow and timing is either "unclear" or any combination of "unclear" with "yes" or "no".

Concerns regarding applicability: high/low/unclear

Are there concerns that the included participants do not match the review question?

High concern: there is high concern that the included participants do not match the review question.

Low concern: there is low concern that the included participants do not match the review question.

If it is unclear.

Are there concerns that the index test, its conduct, or interpretation differ from the review question?

High concern: there is high concern that the conduct or interpretation of the transient elastography test differs from the way it is likely to be used in clinical practice.

Low concern: there is low concern that the conduct or interpretation of the transient elastography test differs from the way it is likely to be used in clinical practice.

If it is unclear.

Are there concerns that the target condition as defined by the reference standard does not match the review question?

High concern: all participants did not undergo liver biopsy for grading hepatic fibrosis.

Low concern: all participants underwent liver biopsy for grading hepatic fibrosis.

If it is unclear.

 

Contributions of authors

Chavdar Pavlov: generated the idea, drafted and revised the protocol, and is a guarantor of the protocol.
Giovanni Casazza: revised the protocol, wrote the statistical section of the protocol, and commented on the protocol.
Dimitrinka Nikolova: drafted and revised the protocol.
Vladimir T Ivashkin: revised the protocol.
Christian Gluud: drafted and revised the protocol.

All authors agreed on the final version of the review protocol.

Declarations of interest

None known.

Sources of support

Internal sources

  • No sources of support supplied

External sources

  • The Editorial Team Office, The Cochrane Hepato-Biliary Group, Copenhagen, Denmark.

Ancillary