Diagnostic Accuracy of Anthropometric and Metabolic Indicators for Predicting MASLD: Evidence from a Large Cohort of Spanish Workers Using FLI and LAP.

Background: Metabolic-dysfunction-associated steatotic liver disease (MASLD) is a major global health concern associated with insulin resistance, metabolic syndrome, and cardiovascular morbidity. Early identification of at-risk individuals through simple, non-invasive methods is essential, particularly in working populations.

Objectives: This study aimed to assess and compare the diagnostic accuracy of four widely used anthropometric and metabolic indicators-body mass index (BMI), waist-to-height ratio (WtHR), triglyceride-glucose index (TyG), and waist-triglyceride index (WTI)-in identifying individuals at risk of metabolic-dysfunction-associated steatotic liver disease (MASLD), as determined by the Fatty Liver Index (FLI) and the Lipid Accumulation Product (LAP), within a large sample of Spanish workers.

Methods: A cross-sectional analysis was performed on data from 386,924 Spanish employees aged between 18 and 69 years. Standardized anthropometric and laboratory measurements were obtained as part of routine occupational medical examinations conducted from 2021 to 2023. The presence of NAFLD was inferred using two validated surrogate markers: FLI and LAP. Receiver operating characteristic (ROC) curves and area under the curve (AUC) values were used to assess the discriminatory ability of each index, stratified by sex.

Results: WTI and TyG demonstrated the highest diagnostic accuracy for both FLI- and LAP-defined NAFLD, with AUC values >0.95 in both sexes. WTI showed the best overall performance, followed closely by TyG. WtHR outperformed BMI but was less accurate than the metabolic indices. Sex-stratified analyses confirmed consistent patterns, with slightly higher AUCs for TyG and WTI in women. BMI consistently yielded the lowest discriminatory performance.

Conclusions: WTI and TyG are superior to BMI and WtHR for non-invasive screening of MASLD in occupational settings. Their simplicity, low cost, and strong predictive value support their integration into routine workplace health surveillance. Sex-specific thresholds and prospective validation are warranted to enhance clinical application.