Diagnostic Performance of Fatty Liver Index for Hepatic Steatosis and its Association With Fibrosis in People Living...

Steatotic liver disease (SLD) and liver fibrosis are significant comorbidities in people living with HIV (PLHIV). Early detection is essential for effective management. This study evaluated the utility of the Fatty Liver Index (FLI) in detecting hepatic steatosis (HS) using Controlled Attenuation Parameter (CAP) measurements as the reference.

This cross-sectional study included 446 PLHIV recruited from Cairo University Hospitals. HS was defined as CAP values exceeding 248 dB/m. FLI cut-off points were determined using the Youden index with bootstrapping validation. Performance metrics and kappa concordance statistics were calculated.

The study cohort (78.7% male, median age 35) showed HS in 27.1% (n = 121) and significant liver fibrosis in 6.5% (n = 29). Optimal FLI cut-off of 45 yielded 71% sensitivity and 72% specificity (receiver operating characteristic = 0.77), while the 60 cut-off provided 57% sensitivity and 80% specificity. Despite similar overall prevalence estimates between methods (30.3% by FLI vs. 27.1% by CAP), significant discordance existed (P < 0.001) with only low-moderate agreement (73.5% agreement, κ = 0.465). Nearly half (49%) of participants with CAP-defined HS were misclassified as having no SLD when using FLI. Importantly, HS was associated with significant liver fibrosis when identified by CAP (P < 0.05) but not when identified by FLI (κ = 0.078, P > 0.05).

FLI demonstrates substantial limitations as a screening tool for HS in people living with HIV, missing nearly half of CAP-defined cases. The poor concordance with CAP and particularly weak performance in lean individuals-who represent a significant proportion of PWH-indicate that FLI cannot reliably identify HS in this population and should not be used as a standalone diagnostic tool.