Association and Diagnostic Performance of the Atherogenic Index of Plasma and Carotid Intima-Media Thickness in Non-alcoholic Fatty Liver Disease: A Cross-Sectional Study

Background: Non-alcoholic fatty liver disease (NAFLD), recently termed metabolic dysfunction-associated steatotic liver disease (MASLD), is increasingly recognized as a multisystem metabolic disorder associated with significantly elevated risk of cardiovascular disease (CVD). Atherogenic Index of Plasma (AIP) and carotid intima-media thickness (CIMT) are considered as surrogate markers of atherosclerotic cardiovascular disease (ASCVD). As CVD is the common link between NAFLD and parameters, such as AIP and CIMT, the present study was conducted to determine any association and discriminatory ability of AIP and CIMT in relation to NAFLD severity. Methods: This was a hospital-based cross-sectional study, conducted in the Department of General Medicine in collaboration with the Department of Radiodiagnosis at Kalinga Institute of Medical Sciences (KIMS), KIIT, Deemed to be University, Bhubaneswar, Odisha, India, from March 2023 to February 2025. A total of 151 participants (75 NAFLD cases and 76 controls) were enrolled during the study. NAFLD was graded by ultrasonography. AIP was calculated as log₁₀(triglyceride (TG)/high-density lipoprotein cholesterol (HDL)-C), Fatty Liver Index (FLI) was derived using the Bedogni formula, and CIMT was measured bilaterally using B-mode ultrasonography. In addition, correlation, multivariate regression, and receiver operating characteristic (ROC) curve analyses were performed. Results: Among 151 participants (75 NAFLD cases and 76 controls), patients with NAFLD demonstrated significantly higher TG and lower HDL-C levels (p<0.001). The AIP was markedly elevated in patients with NAFLD compared to controls (0.82±0.24 vs. 0.42±0.17, p<0.001). Bilateral CIMT values were significantly greater in patients with NAFLD than in controls (right: 1.01±0.36 mm vs. 0.63±0.07 mm; left: 1.02±0.40 mm vs. 0.62±0.10 mm; p<0.001). Across ultrasound-defined NAFLD grades, TGs, AIP, and FLI increased progressively, whereas HDL-C declined significantly (p<0.001 for trend). FLI showed strong positive correlations with CIMT (right: ρ=0.607; left: ρ=0.663; p<0.001). Multivariate regression identified body mass index (BMI), TGs, HDL-C, AIP, and CIMT as independent determinants of NAFLD severity. The ROC analysis demonstrated excellent diagnostic performance for AIP (area under the curve (AUC) = 0.917) and combined AIP+CIMT (AUC = 0.951), indicating high discriminatory accuracy for identifying NAFLD. Conclusions: NAFLD is strongly associated with increased atherogenic burden and subclinical carotid atherosclerosis. AIP and CIMT correlate with disease severity and demonstrate good diagnostic utility in identifying advanced NAFLD. These findings reinforce the systemic cardiometabolic nature of NAFLD and support the potential role of simple lipid indices and vascular imaging in early CVD risk stratification.