Liver fibrosis is the center of diagnosis and management of essentially all chronic liver diseases. While liver biopsy examination still has a role in diagnosis and drug development, it is replaced by non-invasive assessments of liver biopsy in majority of the clinical scenarios. Radiological approaches, namely transient elastography, acoustic radiation force impulse imaging, shear wave elastography, magnetic resonance elastography provide accurate diagnosis of advanced fibrosis and cirrhosis. Serum test formulae based on common laboratory parameters or more specialized parameters including those commercially available panels FibroTest®, FibroMeter® and Enhanced Liver Fibrosis are also available. Combining different modalities may further improve the accuracy. The role of all these non-invasive assessments has been further expanded from diagnostic to prognostic, e.g. risk prediction of hepatocellular carcinoma (HCC) by LSM-HCC score. Treatment of liver fibrosis can be achieved by controlling the underlying diseases, with chronic viral hepatitis as the most established disease model. Currently there are multiple clinical trials evaluating different treatment options to improve fibrosis in patients with non-alcoholic fatty liver disease. Specific anti-fibrotic treatment targets e.g. direct downregulation of hepatic stellate cell, collagen synthesis inhibitors and transforming growth factor-β antagonists have been tested in laboratory and pending further studies in clinical settings.
Liver fibrosis is the formation of scar tissue in response to parenchymal injury secondary to chronic liver disease, e.g. chronic hepatitis B and C, non-alcoholic fatty liver disease (NAFLD) or alcoholism. It distorts the normal liver parenchyma.[
There are varieties of methods for making the diagnosis of liver fibrosis, which can be classified into invasive and non-invasive approaches.
For invasive approach, it refers to liver biopsy examination, which provides liver tissue for a histopathological assessment of liver. Liver biopsy examination can be done percutaneously, transvenously (either transjugularly or transfemorally), or surgically (open or laparoscopic operations).[
Liver biopsy is still regarded as the gold standard for liver fibrosis assessment in various chronic liver diseases.[
Apart from liver fibrosis staging, liver biopsy can provide different information important for the management of the clinicians. For example, in cases of NAFLD, the degree of necroinflammation and steatosis can be determined by liver biopsy so corresponding management can be provided for this potentially reversible situation.[
Such a direct and useful method bears quite a few limitations. Sampling error is a major limitation for liver biopsy as only 1/50,000 of the whole liver parenchyma is obtained. Sampling error can be minimized by either obtaining a specimen of sufficient size (at least 2 cm in length) or from different lobes, which may not be feasible all the time.[
Radiological assessments are either ultrasonographic-based [e.g. transient elastography, acoustic radiation force impulse (ARFI) imaging and shear wave elastography (SWE)] or magnetic resonance (MR)-based [i.e. MR elastography (MRE)].
Transient elastography (Fibroscan®, Echosens, Paris, France) assesses liver stiffness measurement (LSM) by transmitting shear wave followed by ultrasound wave through a probe putting on the skin overlying the liver parenchyma. The velocity of the shear wave passing through the liver parenchyma is calculated by Doppler technique. The higher the velocity, the stiffer the liver parenchyma is. As mentioned by the manufacturer, for an examination to be considered as reliable, it requires at least 10 successful attempts and the ratio of interquartile range to median of those measurements should be less than 0.3.[
ARFI is another technique for estimating liver fibrosis. It is implemented in current ultrasound scanner, without acquirement of external equipment. The conventional ultrasound probe automatically produces an acoustic “push” pulse for generating shear-wave which passes through the tissue. The wave propagation speed is assessed. Again, higher the speed, higher the liver stiffness measurement is.[
SWE is a 2-dimensional ultrasound technique based on the estimation of shear wave velocity from the radiation force of a focused beam of ultrasound,[
MRE adopts a phase contrast imaging method which depends on mechanical wave propagation to assess the degree of liver stiffness.[
Another commonly adopted non-invasive assessment is based on serum with or without clinical parameters. Examples including common parameters in clinical practice include aspartate aminotransferase (AST) to platelet ratio index (APRI),[
Serum test formulae for liver fibrosis
Parameters or index | Formula |
---|---|
APRI | AST (ULN) × 100 / platelet (109/L) |
Forns index | 7.811 − 3.131 × ln(platelet count) + 0.781 × ln(GGT) + 3.467 × ln(age) - 0.014 × (cholesterol) |
FIB-4 | Age (years) × AST [U/l] / (platelets [109/L] × (ALT [U/L])1/2) |
Fibro index | 1.738 − 0.064 × platelet [109/L]) + 0.005 × AST [IU/L] + 0.463 × gamma globulin [g/dL] |
Hui index | exp(3.148 + 0.167 × BMI + 0.088 × bilirubin [μmol/L] - 0.151 × albumin [g/L] − 0.019 × platelet [109/L]) / (1 + exp(3.148 + 0.167 × BMI + 0.088 × bilirubin [μmol/L] − 0.151 × albumin [g/L] - 0.019 × platelet [109/L])) |
NFS | −1.675 + 0.037 × age (years) + 0.094 × BMI (kg/m2) + 1.13 × impaired fasting glycaemia or diabetes (yes = 1, no = 0) + 0.99 × AST/ALT ratio − 0.013 × platelet (× 109/L) − 0.66 × albumin (g/dL) |
BAAT score | BMI (≥ 28 = 1, < 28 = 0) + age at liver biopsy (≥ 50 years = 1, < 50 = 0) + ALT (≥ 2 × (ULN) = 1, < 2 × ULN = 0) + serum triglycerides (≥ 1.7 mmol/L = 1, < 1.7 = 0) |
ALT: alanine aminotransferase; APRI: aspartate aminotransferase to platelet ratio index; AST: aspartate aminotransferase; BAAT: BMI, age, ALT, triglycerides; BMI: body mass index; FIB-4: fibrosis-4; GGT: gamma-glutamyl transferase; NFS: non-alcoholic fatty liver disease (NAFLD) fibrosis score; ULN: upper limit of normal
Some specific biochemical parameters related to fibrinolysis or fibrinogenesis are developed to improve the specificity of liver fibrosis assessment
Different non-invasive approach
Non-invasive tests | Features | Advantages | Disadvantages |
---|---|---|---|
Radiological | |||
Transient elastography | Ultrasound-based liver stiffness measurement by shear wave velocity by a specific probe | Useful across different liver disease entity. Special probes designed for different body built. Measure liver fat at the same time with CAP. Can identify no or minimal fibrosis | Less reliable in obese patients. Less reliable in severe acute exacerbation of hepatitis. Less reliable in post-treatment fibrosis stages in CHB or CHC patients |
Acoustic radiation force impulse imaging | Ultrasound-based wave propagation speed measurement by conventional probe | No additional apparatus except ultrasound machine. Can reflect disease progression. Real-time results. Less technical difficulties. Accurate in overweight or obese patients | Narrow range of measurement. Difficult to define a cut-off. More experienced operators need |
Shear wave elastography | Ultrasound measurement of shear wave velocity | No additional apparatus except ultrasound machine. Elasticity can be reflected by numbers or colors. Sensitive for early-stage fibrosis. Results can be expressed into kPa or m/s | Limited studies on its clinical application |
Magnetic resonance elastography | Phase contrast imaging depending on mechanical wave propagation | Less operator-dependent and less technical failure. Limited effect by obesity or ascites. Can assess complications. Sensitive for early-stage fibrosis. Reproducible results | High cost. Limited availability in some countries/ regions. More time-consuming. Not applicable on patients with iron overload or hemochromatosis. Limited studies on its clinical application |
Serum test formulae | |||
Common laboratory parameters | Refer to Table 1 | Results from routine liver function test, convenient to perform. No inter-observer variations | Cannot be used for all chronic liver diseases |
FibroTest | Consists of GGT, total bilirubin, α-2 macroglobulin, apolipoprotein A1, and haptoglobin | Useful in different chronic liver disease. Reliable. Applicable. Accurate in overweight or obese patients | Suboptimal for early stage fibrosis |
FibroMeter | First 2 generations: consists of platelets, prothrombin index, AST, α-2 macroglobulin, hyaluronate, urea and age. 3rd generation (3G): hyaluronate does not take into account | With high fibrosis classification accuracy. Good predictive value for severe fibrosis in different liver disease entities | High cost |
Enhanced liver fibrosis | Consists of 3 direct blood markers: procollagen III amino terminal peptide, hyaluronic acid and tissue inhibitor of metalloproteinase I | Good prognostic factor for clinical outcomes in patients with chronic liver diseases. Similar results by using fresh blood or cryopreserved blood. Sensitive for advanced fibrosis or cirrhosis | Not sensitive for early stages of fibrosis. Age, low CD4+ T-cell count and other factors can affect ELF results |
AST: aspartate aminotransferase; CAP: controlled attenuation parameter; CHB: chronic hepatitis B; CHC: chronic hepatitis C; ELF: enhanced liver fibrosis
FibroMeter® (Echosens, Paris, France) has been validated in patients with CHB, CHC, NAFLD and alcoholic liver disease.[
Enhanced liver fibrosis (ELF) score is an algorithm consists of 3 direct markers in blood, namely procollagen III amino terminal peptide (PIIINP), hyaluronic acid and tissue inhibitor of metalloproteinase I (TIMP-I).[
There are some other novel serum fibrosis markers that raise the attention of the clinicians. Glycosylated Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA+-M2BP) is a marker which is related to fibrosis-related glyco-alteration. It can be measured by a glycan-based immunoassay, FastLec-Hepa. A cut-off index would be calculated based on the measured value.[
It is common for using both radiological and biochemical methods to increase the accuracy in determining the degree of fibrosis. Both types of methods can play a supplementary role to each other. For example, the performance of ELF improves with the assistance of transient elastography.[
The role of all these non-invasive tests is moving from diagnostic to prognostic. They are useful to predict liver-related complications and hence the prognosis of patients with chronic liver diseases. For example, a LSM with 13.6 kPa can be a predictive value the presence of portal hypertension.[
Survival for chronic liver disease can be predicted using non-invasive test. LSM[
There is good evidence show the strong predictive and even diagnostic role of the non-invasive tests for HCC. ARFI is used for differentiating benign and malignant liver tumors by the assessment of virtual touch tissue imaging (VTI) and virtual touch tissue quantification (VTQ), as VTI appears to be stiffer and VTQ is higher in malignant lesion than its benign counterpart.[
With very potent antiviral agents, patients with chronic viral hepatitis often have liver fibrosis and even cirrhosis regressed after sustained viral suppression or viral clearance.[
There is ample evidence to support the fact that effective antiviral treatment reverses liver fibrosis in majority of CHB patients.[
Importance of metabolic factors on liver fibrosis regression was also supported by data from Chinese and Korean cohorts established that metabolic syndrome is a risk factor of advanced liver fibrosis and cirrhosis independent of viral factors in CHB.[
Indirect evidence of antiviral treatment reversing liver fibrosis also came from two studies using serial LSM results to assess the change in liver fibrosis in large cohorts of asymptomatic CHB patients revealed low incidence rate of liver fibrosis progression, defined as an increase in LSM by 30% or more.[
Data from last century illustrated the conventional interferon regresses liver fibrosis in CHC patients with sustained virologic response (SVR).[
Now it is the era of direct-acting antiviral (DAA) agents in treating CHC patients, which leads to an SVR close to 100%.[
Similar to chronic viral hepatitis, controlling underlying metabolic risk factors is central in the management to improved liver fibrosis in NAFLD patients. A weight reduction of 10% or more by aggressive lifestyle modification appears to resolve fibrosis in most if not all cases (at least with mild-moderate fibrosis).[
In terms of pharmacological agents, there has been much interest in anti-fibrotic therapy in NAFLD as fibrosis is one of the strongest prognostic markers for NAFLD. Lysyl-oxidase like 2 (LOXL2) is involved in a relatively late step in hepatic fibrogenesis, the crosslinking of extracellular matrix proteins such as collagen and elastin.[
Active clinical trials in the clinical trials.gov on anti-fibrotic treatments
Clinicaltrials.gov | Drug | Phase | Disease | Target sample size | Status |
---|---|---|---|---|---|
NCT01965418 | Fufang Biejia Ruangan | 4 | Chronic hepatitis B | 100 | Recruiting |
NCT02241616 | Entecavir + Fuzheng Huayu + TCM Granule | 4 | Chronic hepatitis B | 350 | Recruiting |
NCT00956098 | Oltipraz | 2 | Chronic hepatitis B or C | 81 | Completed |
NCT02138253 (POLT-HCV-SVR) | IDN-6556 | 2 | Chronic hepatitis C | 60 | Ongoing, finished recruitment |
NCT02744105 | Dietary Supplement: Spirulina | N/A | Chronic hepatitis C (in beta-thalassemia) | 60 | Ongoing, finished recruitment |
NCT02217475 | Cenicriviroc | 2 | NASH fibrosis | 200 | Ongoing, finished recruitment |
NCT03059446 | Cenicriviroc | 2 | NASH fibrosis | 200 | Recruiting by invitation |
NCT03028740 (AURORA) | Cenicriviroc | 3 | NASH fibrosis | 2000 | Recruiting |
NCT02530138 | Synbiotic | 2/3 | NASH fibrosis | 42 | Recruiting |
NCT02686762 | Emricasan | 2 | NASH fibrosis | 330 | Recruiting |
NCT02704403 (RESOLVE-IT) | Elafibranor | 3 | NASH fibrosis | 2000 | Recruiting |
NCT02548351 (REGENERATE) | Obeticholic Acid | 3 | NASH fibrosis | 2000 | Recruiting |
NCT03053050 (STELLAR 3) | Selonsertib | 3 | NASH advanced fibrosis | 800 | Recruiting |
NCT03053063 (STELLAR 4) | Selonsertib | 3 | NASH cirrhosis | 800 | Recruiting |
NCT01899859 | GR-MD-02 | 1 | NASH cirrhosis | 31 | Completed |
NCT02462967 | GR-MD-02 | 2 | NASH cirrhosis | 156 | Ongoing, finished recruitment |
NCT02806011 | Livercellgram | 2 | Alcoholic cirrhosis | 50 | Recruiting by invitation |
NCT01452308 | Simtuzumab | 2a | Any | 20 | Completed |
NASH: non-alcoholic steatohepatitis
Cenicriviroc is a C-C chemokine receptor type 2 and type 5 (CCR2/CCR5) antagonist, which interrupts the inflammatory cascade in NASH that leads to fibrogenesis. In animal models, the drug has been shown to have anti-inflammatory and anti-fibrotic activity.[
Ursodeoxycholic acid (UDCA) was found to reduced serum ALT, GGT and PIIIP in an early study.[
Hepatic stellate cells (HSC) are the main collagen-producing cells in the liver and their activation promotes liver fibrosis. Targeting HSC is a popular strategy for treating liver fibrosis.[
Several novel targets have been identified for the treatment of liver fibrosis through suppression of HSC activation. Interleukin (IL)-30 attenuates hepatic fibrosis by inducing natural killer group 2D (NKG2D)/ribonucleic acid export 1 crosstalk between activated HSCs and natural killer T cells and is therefore an ideal therapy for liver fibrosis. Hydrogen peroxide-inducible clone-5 (Hic-5), a transforming growth factor (TGF)-β1-inducible focal adhesion protein, facilitates cell proliferation, ECM expansion and vascular restoration and restructuring.[
Although several drugs show potent anti-fibrotic activities in experimental models of hepatic fibrosis, there is presently no effective pharmaceutical intervention specifically approved for the treatment of liver fibrosis. Targeted delivery systems that bind specifically to receptors solely expressed on activated HSCs or trans-differentiated MFBs are essential to increase treatment efficacy as well as to reduce adverse effects. The applicability and efficacy of sequestering molecules, selective protein carriers, lipid-based drug vehicles, viral vectors, transcriptional targeting approaches, therapeutic liver- and HSC-specific nanoparticles, and miRNA-based strategies are potential and promising treatment strategies.[
Continuous accumulation of extracellular matrix (ECM) extremely rich in collagen I and III in response to liver injury leads to scar deposition and liver fibrosis.[
Halofuginone is an analog of febrifugine - an alkaloid originally isolated from the plant Dichroa febrifuga.[
TGF-β1 is the key pro-fibrogenic cytokine involved in liver fibrosis, as it regulates the production and deposition of ECM.[
CTGF is a mediator of ECM accumulation and coordinates a late common pathway to fibrosis.[
With the wide applicability of non-invasive assessments of liver fibrosis, the management of 2 billion patients with chronic liver diseases worldwide has been revolutionized. While liver biopsy examination still has an important role in the diagnostic process, non-invasive assessments including transient elastography and serum biomarkers have high accurate to diagnose advanced fibrosis and cirrhosis. Transient elastography and serum biomarkers can be used alone or in combination, either simultaneously or in a stepwise approach. Meanwhile, ARFI and SWE are effective for staging liver fibrosis, especially when ultrasound is the first imaging tool for assessment of diffuse liver disease. Treating underlying chronic liver diseases is still the cornerstone of liver fibrosis regression. Potent antiviral treatments for chronic viral hepatitis lead to regression of liver fibrosis and even cirrhosis in majority of patients. Numerous ongoing clinical trials in NAFLD patients will bring us treatment to treat NASH fibrosis and cirrhosis soon. Plentiful therapeutic agents specifically targeting the fibrogenesis pathways, in particulars HSC and TGF-β1 work well in animal models. We look forward to assess these agents in human and hopefully they can modify the natural history of chronic liver diseases, and more importantly, to improve patient outcome in the near future.
Drafting of the manuscript: J.Y.K. Cheng, G.L.H. Wong
Critical revision of the manuscript for important intellectual content: J.Y.K. Cheng, G.L.H. Wong
None.
Grace L.H. Wong has served as an advisory committee member for Gilead Sciences. She has also served as a speaker for Abbott, Abbvie, Bristol-Myers Squibb, Echosens, Furui, Gilead Sciences, Janssen and Roche.
Not applicable.
Not applicable.