Aim: To determine the discriminatory performance of fatty liver index (FLI) for non-alcoholic fatty liver disease (NAFLD).
Methods: The data of 5052 subjects aged over 18 years were analyzed. FLI was calculated from body mass index, waist circumference (WC), triglyceride, and gamma glutamyl transferase data. Logistic regression analysis was conducted to determine the association between FLI and NAFLD. The discriminatory performance of FLI in the diagnosis of NAFLD was evaluated by receiver operating characteristic analysis. Area under the curves (AUCs) and related confidence intervals were estimated. Optimal cutoff points of FLI in the diagnosis of NAFLD were determined based on the maximum values of Youden's index.
Results: The mean age of men and women in the study population were 44.8 ± 16.8 and 43.78 ± 15.43, respectively (P = 0.0216). The prevalence of NAFLD was 40.1% in men and 44.2% in women (P < 0.0017). FLI was strongly associated with NAFLD, so that even a one unit increase in FLI increased the chance of developing NAFLD by 5.8% (OR = 1.058, 95%CI: 1.054-1.063, P < 0.0001). Although FLI showed good performance in the diagnosis of NAFLD (AUC = 0.8656 (95%CI: 0.8548-0.8764), there was no significant difference with regards to WC (AUC = 0.8533, 95%CI: 0.8419-0.8646). The performance of FLI was not significantly different between men (AUC = 0.8648, 95%CI: 0.8505-0.8791) and women (AUC = 0.8682, 95%CI: 0.8513-0.8851). The highest performance with regards to age was related to the 18-39 age group (AUC = 0.8930, 95%CI: 0.8766-0.9093). The optimal cutoff points of FLI were 46.9 in men (sensitivity = 0.8242, specificity = 0.7687, Youden's index = 0.5929) and 53.8 in women (sensitivity = 0.8233, specificity = 0.7655, Youden's index = 0.5888).
Conclusion: Although FLI had acceptable discriminatory power in the diagnosis of NAFLD, WC was a simpler and more accessible index with a similar performance.
Keywords: Body mass index; Discriminatory performance; Fatty liver index; Non-alcoholic fatty liver disease; Optimal cutoff points; Waist circumference.