Non-invasive diagnosis of non-alcoholic steatohepatitis and advanced fibrosis in Japan: A targeted literature review.

Despite the invasive nature of liver biopsy, it remains the current standard for diagnosing non-alcoholic steatohepatitis (NASH) and fibrosis staging. Given the rising prevalence of non-alcoholic fatty liver disease (NAFLD) in Japan, there is a need for reliable non-invasive tests to accurately and efficiently identify NASH and advanced (F3/F4) fibrosis. A review of published works from English and Japanese sources was undertaken in PubMed, Embase, and Ichushi Web to identify studies reporting diagnostic characteristics of NITs in biopsy-proven Japanese NAFLD/NASH patients including sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the receiver operating characteristic curve. The performance of non-invasive tests for two diagnostic questions were assessed, namely: (i) identifying NASH cases among NAFLD; and (ii) distinguishing advanced fibrosis (F3-4) from milder fibrosis (F0-2). Twenty-five studies reported outcomes for serum biomarkers, imaging, scoring systems, and novel complex techniques (based on multivariable regression models) for both diagnostic questions. Serum biomarkers were the most commonly assessed method for NASH identification, whereas scoring systems and imaging techniques were most commonly studied for fibrosis staging. In general, tests for NASH identification showed higher PPVs than NPVs, suggesting their usefulness in identifying probable NASH cases. The reverse was observed for fibrosis staging, with higher NPVs than PPVs, suggesting their use in excluding patients at low risk of F3/F4 disease rather than identifying definite F3/F4 fibrosis. In Japanese studies, simple scoring systems and imaging techniques showed particular usefulness in prediction of fibrosis staging, and combinations of serum biomarkers showed diagnostic potential for NASH screening.