The utility of the NAFLD Fibrosis Score in morbidly obese subjects with NAFLD

Background To date, the noninvasive diagnostic tests for hepatic fibrosis in subjects with nonalcoholic fatty liver disease (NAFLD) have proven to be suboptimal. We evaluated the validity of a recently proposed NAFLD fibrosis score to identify liver fibrosis in morbidly obese individuals with elevated and normal alanine aminotransferase (ALT) levels. Methods Medical records of 401 patients that underwent a gastric bypass operation and intraoperative liver biopsy were analyzed. Three hundred thirty one patients with biopsy-proven NAFLD were included in the study (group A). These patients were divided into two ALT groups based on their levels according to the new proposed normal range: group B elevated level (ALT>19 U/L in females and > 30 U/L in males, n=221) and group C normal ALT (n=110). Diagnostic accuracy of the system was assessed for the presence/absence of any fibrosis, significant fibrosis (stage 2-4), and advanced fibrosis (stages 3 and 4) in all of the groups. Results The prevalence of advanced fibrosis in our cohort was about 14%. The low NAFLD fibrosis score demonstrated high accuracy for ruling out advanced fibrosis, with negative predictive value (NPV) of 98 and 99% in groups A and B, respectively. The NPV for significant fibrosis in groups A, B, and C was 87, 88, and 88%, respectively. The respective positive predictive value for the high NAFLD fibrosis score for the presence of any fibrosis was 88, 95, and 77% in groups A, B, and C. Conclusions The NAFLD fibrosis score may be a useful noninvasive approach for excluding significant and advanced fibrosis and in morbidly obese patients.