Association between the atherogenic index of plasma and metabolic-associated/nonalcoholic fatty liver disease: a systematic review and meta-analysis

Background: MAFLD-previously termed NAFLD-has emerged as the most common condition on a global scale. Obesity, insulin resistance, dyslipidemia, and atherosclerosis are closely linked to its pathogenesis. Lipid dysregulation, insulin resistance, and inflammatory status are reflected by the atherogenic index of plasma (AIP), computed as the logarithmic ratio of triglycerides to HDL-C. Although multiple studies have suggested an association between AIP and MAFLD/NAFLD, the reported findings remain inconsistent. The present investigation sought to synthesize available evidence regarding the AIP-MAFLD/NAFLD relationship and to appraise the diagnostic accuracy of AIP. Methods: This systematic review and meta-analysis was conducted in accordance with the PRISMA 2020 statement. PubMed, Embase, the Cochrane Library, and Web of Science were searched through October 2025. Fixed- or random-effects models were applied according to heterogeneity. Weighted mean difference (WMD) and pooled odds ratios (ORs) were calculated. Diagnostic performance was evaluated using a bivariate random-effects model to obtain pooled sensitivity, specificity, and summary receiver operating characteristic (SROC) curves. Subgroup analyses were performed by diagnostic criteria, age, diabetes status, BMI, and region. Meta-regression explored the influence of demographic and metabolic covariates. Sensitivity analyses and publication bias assessment using Egger regression and Deeks' asymmetry test were also conducted. Results: Twenty observational studies involving 245,571 adults were included. AIP levels were significantly higher in MAFLD/NAFLD patients than in controls (WMD = 0.26; 95% CI: 0.21-0.30). Elevated AIP was significantly associated with MAFLD/NAFLD risk (pooled odds ratio = 3.18; 95% CI: 2.54-3.98). Subgroup analyses demonstrated greater consistency in studies using MAFLD diagnostic criteria and among obese populations. Diagnostic meta-analysis using a bivariate random-effects model yielded a pooled sensitivity of 0.73 and specificity of 0.65, with a summary AUC of 0.75 (95% CI: 0.71-0.79), indicating moderate diagnostic accuracy. Sensitivity analyses confirmed robustness, and no significant publication bias was detected. Conclusions: Elevated AIP is significantly associated with increased MAFLD/NAFLD risk and shows moderate diagnostic performance. As a simple and cost-effective index derived from routine lipid profiles, AIP may serve as a useful early screening tool for individuals at elevated risk of fatty liver disease and cardiometabolic comorbidities. Further prospective studies are warranted to clarify causality and clinical utility. Systematic review registration: https://www.crd.york.ac.uk/PROSPERO/home, identifier CRD42025116919.