Evaluation of Leptin, Adiponectin, and the Leptin/Adiponectin Ratio as Diagnostic Biomarkers for Metabolic Syndrome

Abstract

Objective: To evaluate serum leptin, adiponectin, and the leptin/adiponectin (L/A) ratio as diagnostic biomarkers for Metabolic Syndrome (MetS) in an Iraqi adult population and to determine optimal cutoff values using receiver operating characteristic (ROC) curve analysis.

Methods: This case-control study enrolled 90 adults (45 MetS cases diagnosed by IDF 2005 criteria and 45 age- and sex-matched healthy controls) from Al-Zahraa General Hospital, Wasit, Iraq, between November 2024 and January 2025. Serum leptin and adiponectin were measured by enzyme-linked immunosorbent assay. Anthropometric and biochemical parameters were assessed under standardised conditions. ROC analysis evaluated diagnostic accuracy, with sensitivity, specificity, area under the curve (AUC), and 95% confidence intervals calculated.

Results: Leptin was significantly elevated in MetS patients compared to controls (9.37 ± 1.77 vs. 2.07 ± 2.06 ng/mL; P < 0.001), while adiponectin was significantly reduced (5.35 ± 2.81 vs. 10.17 ± 7.14 µg/mL; P < 0.001). The L/A ratio was markedly higher in cases (2.07 ± 0.81 vs. 0.18 ± 0.08; P < 0.001). ROC analysis revealed AUC values of 0.981 (95% CI: 0.959–1.000) for leptin, 0.843 (95% CI: 0.757–0.929) for adiponectin, and 1.000 (95% CI: 1.000–1.000) for the L/A ratio. At a cutoff >0.52, the L/A ratio achieved 100% sensitivity and 100% specificity.

Conclusion: The L/A ratio demonstrated excellent discriminative ability for MetS, outperforming either adipokine alone. This composite biomarker holds promise for screening and risk stratification, though validation in larger, independent cohorts is warranted.