Complete Blood Count-Derived Inflammatory Indices in Prediabetes: A Head-to-Head Comparison

Background: Chronic low-grade inflammation contributes to early glucose dysregulation, but comparative evidence on complete blood count-derived inflammatory indices in prediabetes remains limited. This study aimed to compare the associations of five complete blood count-derived inflammatory indices with prediabetes and to assess their discriminative performance. Methods: In this retrospective cross-sectional study, 255 adults (128 with prediabetes and 127 with normoglycemia) were identified from 12,540 individuals screened at the internal medicine outpatient clinics of a university hospital. The neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, systemic immune-inflammation index, and systemic inflammation response index were compared between groups. Adjusted logistic regression, hierarchical regression, and receiver operating characteristic curve analyses were performed. Results: All indices except the monocyte-to-lymphocyte ratio were significantly higher in the prediabetes group (all p < 0.001). Among the evaluated indices, the neutrophil-to-lymphocyte ratio showed the strongest association with prediabetes, with the largest standardized odds ratio (2.691; 95% confidence interval, 1.839–3.938) and the highest explanatory power (Nagelkerke R2 = 0.326). Its addition to the base model significantly improved model fit (likelihood ratio χ2 = 33.62, p < 0.001), and the association remained significant after adjustment for body mass index, C-reactive protein, and lipid parameters. It also yielded the highest area under the curve (0.714). Conclusions: In this cross-sectional analysis, the neutrophil-to-lymphocyte ratio showed the most robust independent association with prediabetes among the evaluated complete blood count-derived inflammatory indices. However, the overall discriminative performance was modest, supporting the use of these indices as adjunctive rather than standalone screening markers.