Discriminative Utility of Peripheral Blood Immune-Inflammatory Indices for Chronic Osteomyelitis: A Single-Center Retrospective Case-Control Study.

OBJECTIVE: This study aims to assess the clinical utility of composite immune-inflammatory indices formed from differential peripheral blood cell counts (NLR, PLR, SIRI, SII, PIV) for the early identification and risk stratification of chronic osteomyelitis, and to investigate potential clinical applications. METHODS: A retrospective unmatched case-control study was conducted at Zhongnan Hospital of Wuhan University. A total of 212 patients with confirmed chronic osteomyelitis and 440 non-infected trauma controls during the same period were enrolled using convenience sampling. Routine complete blood count data and main clinical information at admission were collected. The five composite indices were calculated and compared between groups. Receiver operating characteristic (ROC) curves and area under the curve (AUC) with 95% confidence intervals (CI) were used to evaluate diagnostic performance, with pairwise AUC comparisons by DeLong's test. Multivariate logistic regression was performed to adjust for potential confounders (age, sex, diabetes, drinking history) and assess independent diagnostic value. RESULTS: Although total white blood cell count did not differ significantly between groups, NLR, PLR, SIRI, SII, and PIV were all significantly elevated in the osteomyelitis group (all P < 0.001). SII and PIV showed higher AUC, sensitivity, and specificity (SII AUC = 0.800, 95% CI: 0.764-0.835; PIV AUC = 0.781, 95% CI: 0.744-0.818). After adjustment for confounders, SII (OR = 1.002, 95% CI: 1.001-1.002) and PIV (OR = 1.002, 95% CI: 1.002-1.003) remained independent predictors. DeLong's test indicated that SII had significantly better diagnostic utility than NLR, PLR, and SIRI, but not significantly different from PIV. CONCLUSION: Composite immune‑inflammatory indices based on peripheral blood counts are clinically accessible and cost‑effective. SII and PIV may serve as potential auxiliary tools for chronic osteomyelitis diagnosis, complementing the limitations of traditional WBC, pending further prospective validation.