Serum interleukin-6 as an inflammatory biomarker in type 2 diabetes mellitus: correlation with diabetic peripheral neuropathy and diagnostic performance

Ahmed Yaseen Abed; Alaa Ahmed Fezea

Ahmed Yaseen Abed Department of Habbaniyah Education, General Directorate of Education in Anbar, Ministry of Education, Anbar, Iraq https://orcid.org/0000-0003-0970-0954
Alaa Ahmed Fezea College of Health and Medical Techniques, University of Al-Maarif, Ramadi, Anbar, Iraq https://orcid.org/0009-0002-9287-1606

Keywords: inflammation, cytokines, Michigan neuropathy screening instrument, cross-sectional studies, roc curve, Iraq

Abstract

Diabetic peripheral neuropathy (DPN) is a common, debilitating complication of type 2 diabetes mellitus (T2DM); interleukin-6 (IL-6) has been increasingly implicated in its pathogenesis, yet Iraqi data remain scarce. We compared serum IL-6 between T2DM patients with and without DPN, assessed its correlation with neuropathy severity, and evaluated its diagnostic performance. A cross-sectional study was conducted on 90 patients with T2DM, equally divided into two groups based on DPN status assessed using the Michigan Neuropathy Screening Instrument (MNSI). Serum IL-6 was measured by ELISA and analysed using the Mann-Whitney U test, Spearman correlation, ROC curve analysis, and multivariable logistic regression. Median serum IL-6 was higher in DPN patients (194.38 pg/mL; IQR: 144.16–338.89) than in those without DPN (97.01 pg/mL; IQR: 71.39–148.26; p<0.001) and correlated strongly with MNSI score (rho=0.693, p<0.001), with no correlation to HbA1c or fasting glucose. IL-6 independently predicted DPN (OR=1.020; 95% CI: 1.010–1.031; p<0.001), with good diagnostic accuracy (AUC=0.843; 95% CI: 0.763–0.922; cut-off 110.34 pg/mL; sensitivity 91.1%; specificity 64.4%). Serum IL-6 is significantly elevated in DPN and correlates with its severity independent of glycaemic control, showing good diagnostic accuracy as a potential adjunctive screening biomarker in resource-limited settings.