Diagnostic Value of Mean Platelet Volume and Hematological Inflammatory Ratios in Brucellosis: A Case-Control Study

Brucellosis diagnosis remains challenging in resource-limited endemic settings. This retrospective case-control study evaluated the diagnostic utility of mean platelet volume (MPV) and hematological inflammatory ratios in brucellosis. Fifty patients with confirmed brucellosis and 50 age-matched healthy controls were included at a university hospital in Turkey (2015-2018). Complete blood count parameters, hematological ratios (neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR], lymphocyte-to-monocyte ratio [LMR]), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were measured at diagnosis. Receiver operating characteristic (ROC) curve analysis evaluated diagnostic performance; multivariate logistic regression developed a combined model. Brucellosis patients showed significantly lower MPV (8.04 ± 0.95 vs. 8.56 ± 0.69 fL, p = 0.002), higher platelet counts (305.0 ± 116.0 vs. 246.0 ± 55.2 × 10³/μL, p = 0.002), lower NLR (median: 1.69 vs. 2.07, p = 0.013), and higher LMR (median: 5.28 vs. 4.12, p = 0.008). ESR demonstrated the best individual diagnostic performance (area under the curve [AUC] = 0.842). The combined model (MPV + ESR + CRP) achieved superior performance (AUC = 0.891, sensitivity 84%, specificity 86%). Limitations include the single-center retrospective design, lack of internal validation, and comparison with healthy controls only. Notably, healthy controls were deliberately selected to establish baseline hematological profiles associated with brucellosis rather than to differentiate it from other infections. Brucellosis presents a unique hematological profile with decreased MPV and altered inflammatory ratios. The combined model offers a potentially cost-effective screening approach for endemic settings, pending external validation.