Retrospective case-control study of haematological indices and inflammatory ratios in the diagnosis of paediatric brucellosis.

Abstract

Background: Brucellosis is a common zoonotic infection in Turkey and other Mediterranean countries. In children, symptoms are usually non-specific, including fever, fatigue, arthralgia, and myalgia, which may complicate diagnosis. Haematological indices and inflammatory ratios have recently been studied as possible supportive markers in infectious diseases, but findings in brucellosis remain inconsistent. This study investigated red cell distribution width (RDW), plateletcrit (PCT), platelet indices, neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) in paediatric brucellosis.

Materials and methods: This retrospective case-control study included 42 children with brucellosis and 39 healthy controls. Patients were followed at Erzurum Regional Training and Research Hospital between September 2018 and February 2019. Diagnosis was based on compatible clinical findings together with a standard tube agglutination (Wright) titer ≥ 1:160, a positive Brucella Coombs test, or isolation of Brucella spp. from blood culture. Complete blood count parameters were measured using a Sysmex XN-series haematology analyser with a DI-60 morphology modüle. Statistical analyses included the t-test or Mann-Whitney U test for continuous variables and chi-square or Fisher's exact test for categorical variables. Benjamini-Hochberg correction was applied for multiple comparisons. ROC curve analysis and age- and sex-adjusted binary logistic regression were also performed.

Results: Thirty patients were male and 12 were female. The median age was 14 years (range 6-17). The most common symptoms were arthralgia (85.7%), weakness (71.4%), and fever (66.7%). RDW, platelet count, and PCT differed significantly between groups in unadjusted analysis, but these differences lost significance after correction for multiple testing (all FDR-adjusted p > 0.18). ROC analysis showed low diagnostic performance overall. RDW demonstrated high specificity (92.3%) but low sensitivity (46.3%). After adjustment for age and sex, only RDW remained independently associated with brucellosis (adjusted OR 2.31, 95% CI 1.30-4.11, p = 0.005). Other haematological indices and inflammatory ratios were not significantly different.

Conclusion: Only RDW remained significantly associated with brucellosis after adjustment for age and sex. RDW may provide supportive information together with clinical and serological findings, although larger studies are needed to confirm these results.