OBJECTIVETo investigate the correlation of serum osteoprotegerin (OPG) with the progression of nonalcoholic fatty liver disease (NAFLD) and the noninvasive prediction and diagnosis of nonalcoholic steatohepatitis (NASH).

METHODSA total of 136 patients with NAFLD were enrolled, and their tissue samples for liver biopsy and serum samples obtained at 1 week after liver biopsy were collected; 83 healthy subjects without the symptoms of fatty liver disease proved by ultrasound examination were enrolled as controls. The physiological indicators including height, body weight, and waist circumference were measured, and body mass index was calculated. The biochemical parameters including alanine aminotransferase (ALT), aspartate aminotransferase (AST), AST/ALT, alkaline phosphatase, gamma-glutamyl transferase, total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol were measured. Double-antibody sandwich enzyme-linked immunosorbent assay was used to determine the serum level of OPG. The rank sum test, chi-square test, t-test, one-way analysis of variance, Spearman correlation analysis, least significant difference test, and receiver operating characteristic (ROC) curve were applied for statistical analysis of various data.

RESULTSSerum OPG level was correlated with AST and TG (P < 0.05), and was highly correlated with hepatocyte fatty degeneration, ballooning degeneration, intralobular inflammation, portal inflammation, and fibrosis degree (P < 0.01). With the increasing NAFLD activity score (NAS), serum OPG level decreased, and there was a highly negative correlation between them (r = -0.928, P < 0.01). Serum OPG level was significantly lower in NASH patients than non-NASH patients. The area under the ROC curve of serum OPG level was 0.963, and according to the Youden index, its optimal sensitivity and specificity were 96.1% and 97.4%, respectively, at an optimal cut-off value of 242.96 ng/L, which suggested a high diagnostic power.

CONCLUSIONIn NASH patients, serum OPG level decreases significantly. Serum OPG level can be used as an independent predictive factor to evaluate NASH and its severity, as well as a noninvasive diagnostic index for NASH.