Published online Jul 7, 2019. doi: 10.3748/wjg.v25.i25.3256
Peer-review started: April 19, 2019
First decision: May 9, 2019
Revised: May 20, 2019
Accepted: June 8, 2019
Article in press: June 8, 2019
Published online: July 7, 2019
Accurate detection of significant fibrosis (fibrosis stage 2 or higher on the METAVIR scale) is important especially for chronic hepatitis B (CHB) patients with high viral loads but with normal or mildly elevated alanine aminotransferase (ALT) levels because the presence of significant fibrosis is accepted as the indication for antiviral treatment. Liver biopsy is the reference standard for diagnosing significant fibrosis, but it is an invasive procedure. Consequently, non-invasive imaging-based measurements, such as magnetic resonance elastography (MRE) or two-dimensional shear-wave elastography (2D-SWE), have been proposed for the quantitative assessment of liver fibrosis.
Liver biopsy is still considered the “gold standard” for the evaluation of significant fibrosis in CHB patients. However, its utilization is often restricted because its invasiveness can cause life‐threatening complications. Moreover, tissue obtained via biopsy represents approximately only 1/50000 of the liver volume, which may result in a sampling error and is associated with considerable interobserver variability in the microscopic evaluation. Furthermore, repeating the liver biopsy to monitor changes in liver fibrotic burden is generally not feasible in clinical practice.
The objective of this study was to evaluate the liver stiffness values of MRE and two-dimensional SWE (2D-SWE) to assess liver fibrosis and to compare their diagnostic performances with those of FIB-4 and APRI for the prediction of significant fibrosis, which is an indicator for initiating antiviral therapy in treatment-naïve CHB patients with high viral loads but with borderline-normal or mildly elevated ALT levels.
The study enrolled 63 treatment-naïve CHB patients with high viral loads but with normal or mildly elevated ALT levels who underwent liver biopsy before a decision was made to initiate antiviral therapy. MRE and 2D-SWE were performed, and serum-based indices, such as FIB-4 and APRI, were calculated. The diagnostic performances of MRE, 2D-SWE, FIB-4, and APRI for assessing significant fibrosis (≥ F2) and cirrhosis (F4) were evaluated with liver histology as the reference standard, using receiver operating characteristic analyses.
The liver fibrosis stage was F0/F1 in 19, F2 in 14, F3 in 14, and F4 in 16 patients, respectively. MRE significantly discriminated F2 from F0/1 (P = 0.022), whereas 2D-SWE showed a broad overlap in distinguishing those stages. MRE showed a higher correlation coefficient value with fibrosis stage than 2D-SWE with fibrosis stage (0.859 vs 0.647, Spearman test; P < 0.001). Multiple-regression analyses showed that fibrosis stage was the only factor affecting the values of MRE (P < 0.001), whereas body mass index (P = 0.042) and fibrosis stage (P < 0.001) were independent factors affecting 2D-SWE values. The MRE performance for diagnosing significant fibrosis was better than FIB-4 (P = 0.002) and APRI (P = 0.010), whereas the performance of 2D-SWE was not significantly different from that of FIB-4 or APRI.
MR elastography might be a non-invasive and more precise measurement for the assessment of significant fibrosis compared to 2D-SWE as well as serum-based indices in treatment-naïve CHB patients with high viral loads but with normal or mildly elevated ALT levels who should be considered for initiation of antiviral therapy depending on the presence of significant fibrosis.
There are some limitations to the present study. First, the use of liver biopsy as the reference standard for assessing liver fibrosis has limitations associated with sampling errors, as well as intra and interobserver variability, which are at least partly linked to the size of the biopsy. Second, despite MRE has the best effectiveness, it is much more expensive than 2D-SWE and is available only in tertiary centers. Third, as the sample size of this study is relatively small, the present results need to be validated independently in further studies.