CRP-to-lymphocyte ratio as a predictor of MRI-confirmed spondylodiscitis in RBT-positive patients with suspected brucellosis.

INTRODUCTION: Brucellosis is a zoonotic infection that is endemic in many regions, including Türkiye. Spondylodiscitis is one of its most significant complications. This study evaluated the association of hematologic parameters, particularly C-reactive protein (CRP) and the CRP-to-lymphocyte count (CRP/LC) ratio, with serological titers and magnetic resonance imaging (MRI)-confirmed spondylodiscitis, and explored their potential role as supportive markers for risk stratification and identifying patients who may benefit from further imaging. METHODOLOGY: This retrospective cross-sectional study analyzed 1,568 patients with positive Rose Bengal test results between 2014 and 2022. Hematologic and serologic data were evaluated, and imaging findings [MRI/computed tomography (CT)] were reviewed for spondylodiscitis. Serum tube agglutination (STA) titers ≥ 1/160 were considered as indicative of acute infection. Statistical methods included correlation, multiple linear regression, receiver operating characteristic (ROC) analysis, and non-parametric tests. RESULTS: STA titers ≥ 1/160 were more frequent in males (68.87%) than females (29.69%) (p < 0.001). CRP, LC, and CRP/LC ratio were significantly higher in patients with elevated STA titers and MRI-confirmed spondylodiscitis. Correlations between hematologic markers and STA titers were generally weak to modest. Multiple linear regression identified CRP and LC as independent predictors of STA titer. ROC analysis showed that CRP (AUC: 0.67; area under the curve) and CRP/LC ratio (AUC: 0.66) had the highest discriminative performance. MRI-confirmed spondylodiscitis was detected in 2.3% patients. CONCLUSIONS: CRP and CRP/LC ratio appear to be useful supportive markers for identifying patients with high STA titers and MRI-confirmed spondylodiscitis and may help clinicians prioritize imaging studies in specific cases.