Clinical and laboratory characteristics of human brucellosis and predictors of focal involvement: a retrospective cohort study from Türkiye

Brucellosis is a zoonotic infection with a wide clinical spectrum, ranging from nonspecific symptoms to severe focal involvement. Focal involvement significantly affects disease prognosis, yet early prediction remains challenging. Easily accessible inflammatory markers may provide a practical solution for early risk stratification. The aim of this study was to evaluate clinical and laboratory factors associated with focal involvement in brucellosis and to investigate the predictive value of inflammatory markers, particularly C-reactive protein (CRP) and neutrophil-to-lymphocyte ratio (NLR).

This retrospective observational study included adult patients diagnosed with brucellosis between January 2021 and December 2025 at a tertiary care center. Focal involvement was defined based on clinical findings confirmed by imaging modalities. Demographic, clinical, epidemiological, and laboratory data were collected. Patients were divided into focal and non-focal groups. Multivariate logistic regression analysis was performed to identify independent predictors. Receiver operating characteristic (ROC) analysis was used to assess predictive performance and determine optimal cut-off values.

A total of 173 patients were included, of whom 54 (31.2%) had focal involvement. Osteoarticular involvement, particularly spondylodiscitis, was the most common presentation. Patients with focal involvement were older and had significantly higher CRP, erythrocyte sedimentation rate, NLR, and MLR levels (p < 0.05). In multivariate analysis, CRP (OR 1.015, 95% CI 1.004–1.028, p = 0.003) and NLR (OR 1.341, 95% CI 1.012–1.778, p = 0.041) were identified as independent predictors. The combined CRP–NLR model demonstrated moderate discriminative ability (AUC: 0.714). Optimal cut-off values were 42 mg/L for CRP and 1.62 for NLR.

Focal involvement in brucellosis is more closely associated with systemic inflammatory response than epidemiological factors. CRP and NLR may serve as cost-effective and clinically useful markers for early identification of patients at risk. Their combined use may support early decision-making and guide the need for further diagnostic evaluation. Larger prospective studies are needed to validate these findings.

Not applicable.