Non-invasive liver tests for fibrosis

Liver biopsy is currently the reference standard for the identification and staging of liver fibrosis, but its role has significantly declined because of several limitations such as invasiveness of the procedure, sampling errors, and intra- and interobserver variability.

The advent of non-invasive tests (NITs) has now replaced the role of liver biopsy. 

These approaches can overcome the limitations of liver biopsy.

Imaging-based elastography and serum biomarkers are currently the two main NITs for liver fibrosis staging. 

Assessments include serology based tests such as the fibrosis-4 (FYB-4) index, NAFLD fibrosis score (NFS), and enhanced liver fibrosis (ELF), or imaging based test such as vibration controlled  transient elastography (VCTE) and magnetic resonance elastography (MRE).

FIB-4 index combines patient age with a basic laboratory tests aspartate amino transferase, ALT, and platelet count to predict liver fibrosis and cirrhosis.

The NFL score combines patient characteristics of age, body mass index, and basic laboratory tests of glucose, aspartate aminotransferase, ALT, albumin, and platelet count.

The ELF scoring system is based on serum tests of inflammatory markers, namely hyaluronic acid, procollagen III,  amino terminal peptide, and tissue inhibitor of matrix metalloproteinase 1.

VCTE is a non-invasive ultrasound based diagnostic modality that detects liver fibrosis and cirrhosis through liver stiffness measurement. 

VCTE accuracy is limited by operator experience, morbid obesity, narrow intercostal space and ascites.

MRE is based on magnetic resonance technique using sheer wave to detect liver fibrosis with very high accuracy.

A VCTE cutoff score of less than 7.7 kPa excludes advanced fibrosis and is  100% sensitive: 100% negative predictive value and leads to 45% fewer liver biopsies.

There are significantly strong positive correlations of liver steatosis values assessed among the three elastography techniques. 

There is a moderate-to-strong correlation between imaging methods and non-invasive serum fibrosis scores. 

Non-invasive tests for liver fibrosis are more desirable and used to improve the diagnosis and prognostication of chronic liver disease of various etiologies. 

However, data on the correlations among three elastography techniques in patients with CLD patients are scarce. 

MRE can be considered the most accurate NIT for detecting liver fibrosis, especially in advanced fibrosis and cirrhosis.

MRE outperforms TE and SWE in detecting stage 4 liver fibrosis in patients with NAFLD.

MRE has an advantage over TE or SWE in that it visualizes the whole liver rather than just small hepatic areas. 

MRE is currently accepted as the most precise NIT for evaluating liver fibrosis, however, ,TE, SWE, APRI, and FIB-4 had a good correlation and can be used particularly in centers with limited availability of MRE. 

Liver necroinflammation influences the increase in liver stiffness as evaluated by imaging-based elastography. 

Viral eradication results in a reduced proportion of patients with advanced fibrosis by 13%, 28%, and 11% based on TE, SWE, and MRE, respectively. 

The reduction of liver stiffness values and serum fibrosis scores after viral eradication were partly caused by the decrease in liver inflammation rather than liver fibrosis regression. 

TE, SWE, and MRE have been extensively validated in a large number of studies. 

In conclusion, TE, SWE, MRE, APRI, and the FIB-4 index have a good correlation. 

Using MRE as the reference standard, all studied NITs have high diagnostic accuracies for detecting liver fibrosis. 





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