Noninvasive Liver Fibrosis Tests in Patients with Nonalcoholic Fatty Liver Disease: An External Validation Cohort

The main aim of this study was the comparative evaluation of nonalcoholic fatty liver disease (NAFLD) fibrosis score (NFS), fibrosis 4 index (FIB-4), AST-to-Platelet Ratio Index (APRI), and enhanced liver fibrosis (ELF) test in distinguishing none/early (F0/F1) from significant/advanced (F2/F3) fibrosis in NAFLD patients, thereby providing an external validation cohort. Thirty-one patients with biopsy-proven NAFLD and 10 matched controls without NAFLD were prospectively enrolled. Serum hyaluronic acid (HA), aminoterminal propeptide of type III procollagen (PIIINP), tissue inhibitor of metallo-proteinases (TIMP)-1, and biochemical tests were measured. NFS, FIB-4, APRI, and ELF were calculated. ELF, FIB-4, and APRI, but not NFS, were higher in F2/F3 than F0/F1 group. Specifically, ELF [area under the ROC curve (AUROC): 0.86 +/- 0.10; p=0.004) and APRI (AUROC: 0.86 +/- 0.07; p=0.005], but not NFS (AUROC: 0.68 +/- 0.12; p=0.16), and FIB-4 (AUROC: 0.71 +/- 0.11; p=0.10), could similarly discriminate F0/F1 from F2/F3 stage. The sensitivity, specificity, positive predicted value (PPV), and negative predicted value (NPV) were: a) for cut-off of APRI=0.5, 85.7%, 70.8%, 46.2%, and 94.4%, respectively, and b) for cut-off of ELF=9.0, 85.7%, 83.3%, 60.0%, and 95.2%, respectively. When ln(PIIINP) or TIMP-1 were combined with APRI, the combined AUROCs could distinguish F2/F3 from F0/F1, but without significantly higher accuracy compared with APRI alone. APRI could also distinguish patients with simple steatosis from nonalcoholic steatohepatitis, and those with from those without lobular inflammation and ballooning, findings warranting further research. In conclusions: The application of ELF test and APRI can distinguish F0/F1 from F2/F3 fibrosis stages in NAFLD patients.