Association of the Arachidonic Acid-to-Eicosapentaenoic Acid Ratio with Metabolic Dysfunction-Associated Steatotic Liver Disease and the Fibrosis-4 Index in Korean Adult Health Check-up Examinees: A Single-Center Cross-Sectional Study

Background: The arachidonic acid-to-eicosapentaenoic acid (AA/EPA) ratio reflects the balance between omega-6 and omega-3 fatty acid pathways and has been discussed as a marker of inflammatory and cardiometabolic status. However, its association with metabolic dysfunction-associated steatotic liver disease (MASLD) and the fibrosis-4 (FIB-4) index remains unclear. This study investigated whether AA/EPA is associated with MASLD status and FIB-4 in Korean adult health check-up examinees.Methods: This single-center cross-sectional study included 392 adult health check-up examinees who underwent abdominal ultrasonography and red blood cell fatty acid testing. MASLD was defined as hepatic steatosis on ultrasonography with at least one cardiometabolic risk factor. FIB-4 was calculated from age, aspartate aminotransferase, alanine aminotransferase, and platelet count. Associations of AA/EPA with MASLD and FIB-4 were evaluated using logistic and linear regression analyses.Results: Among 392 participants, 203 (51.8%) met MASLD criteria. AA/EPA was not associated with MASLD after multivariable adjustment (adjusted odds ratio [OR], 1.02; 95% confidence interval [CI], 0.98–1.06). In contrast, AA/EPA was inversely associated with continuous FIB-4 after adjustment for cardiometabolic covariates, with chronological age excluded to avoid mathematical overlap with the FIB-4 equation (adjusted β=–0.02; 95% CI, –0.03 to –0.01). In exploratory component analyses, AA/EPA was not significantly correlated with aspartate aminotransferase or alanine aminotransferase, whereas it was positively correlated with platelet count.Conclusions: AA/EPA was not associated with MASLD status, whereas it was inversely associated with FIB-4. Category-based analyses supported the direction of this association, and component analyses suggested that platelet-related variation may partly contribute to the FIB-4 finding. These results do not support AA/EPA as a simple MASLD screening marker. Further studies incorporating direct fibrosis assessment, platelet-related parameters, and detailed dietary or supplement information are needed.