Interleukin-6 as a biological marker in keratoconus patients

Background Keratoconus (KC) is a progressive corneal ectasia traditionally viewed as noninflammatory. However, emerging evidence suggests an inflammatory component involving cytokines such as interleukin-6 (IL-6). Objectives To evaluate serum IL-6 levels in cases with KC and determine its diagnostic and predictive value. Patients and methods This comparative cross-sectional study included 25 KC cases and 25 age-matched and sex-matched healthy controls. All participants underwent a full ophthalmologic assessment, including Sirius topography. Serum IL-6 levels were measured using enzyme-linked immunosorbent assay. Results KC cases showed significantly lower intraocular pressure (13±3 vs. 15±3 mmHg, P =0.019), steeper keratometric readings (K1: 46.5±6.71 vs. 42.28±1.77 D, P =0.005; K2 and K-max: both 50.2±7.1 vs. 43.8±1.96 D, P <0.001), and thinner corneas (450±59 vs. 537±36 μm, P <0.001). Serum IL-6 levels were substantially elevated in KC cases (99±33 vs. 58±10 ng/l, P <0.001). Receiver operating characteristic analysis revealed IL-6 could predict KC with an area under the curve of 0.899; a cutoff of more than 73 ng/l yielded 84% sensitivity and 96% specificity. For high-grade KC, IL-6 had moderate predictive ability (area under the curve=0.745; cutoff >110 ng/l). Logistic regression showed each 1 ng/l increase in IL-6 increased KC risk by 9.9% (odds ratio=1.099; 95% confidence interval: 1.032–1.169; P =0.003). Conclusion Serum IL-6 is elevated in KC cases and is considered a valuable biomarker for diagnosis and assessment of disease severity.