RDW only blood marker linked to paediatric brucellosis in small retrospective study

In a retrospective case–control study of 81 children, red cell distribution width (RDW) was the only measured haematological index that remained significantly associated with paediatric brucellosis after adjustment for age and sex. The finding emerged from an analysis of blood counts and inflammation-related ratios in 42 children diagnosed with brucellosis and 39 healthy controls. RDW showed high specificity but low sensitivity in the study’s diagnostic evaluation, meaning it may be most useful as supplementary information rather than a stand-alone test. The authors said larger studies are needed to confirm the result.

The children with brucellosis were followed at Erzurum Regional Training and Research Hospital in Turkey between September 2018 and February 2019. Their median age was 14 years, with a range of six to 17 years; 30 were boys and 12 were girls. Brucellosis was diagnosed through a combination of compatible clinical findings and microbiological or serological evidence. Criteria included a standard tube agglutination, or Wright, titre of at least 1:160, a positive Brucella Coombs test, or isolation of Brucella species from blood culture. The most frequently reported symptoms were arthralgia, present in 85.7% of cases, weakness in 71.4%, and fever in 66.7%.

Researchers used a Sysmex XN-series haematology analyser with a DI-60 morphology module to assess red cell distribution width, platelet count, plateletcrit and other platelet indices. They also examined neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios as potential supportive markers. Continuous variables were compared with t-tests or Mann–Whitney U tests, while categorical variables were assessed using chi-square or Fisher’s exact test. Because the analysis covered multiple comparisons, the researchers applied Benjamini–Hochberg false-discovery-rate correction. They also used receiver operating characteristic curve analysis to assess diagnostic performance and age- and sex-adjusted binary logistic regression to estimate associations with disease status.

RDW, platelet count and plateletcrit differed significantly between the patient and control groups in unadjusted analyses. None of those differences remained significant after correction for multiple testing, with all false-discovery-rate-adjusted p-values greater than 0.18. The diagnostic analysis also found that RDW alone had limited overall performance: its sensitivity was 46.3%, while its specificity reached 92.3%. In other words, the marker would have missed more than half of the children with confirmed disease in this sample, although a positive result was uncommon among the healthy controls.

After the researchers adjusted for age and sex, RDW was the only haematological index or inflammatory ratio independently associated with brucellosis. Its adjusted odds ratio was 2.31, with a 95% confidence interval of 1.30–4.11 and p = 0.005. The remaining platelet indices, neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio were not significantly different. The study does not establish that changes in blood-cell measurements cause brucellosis, nor does it validate RDW as a replacement for clinical assessment, culture or established serological testing. Its retrospective design, small groups, single-centre setting and limited range of ages also constrain how broadly the association can be applied.

Subject of Research: Assessment of haematological indices and inflammatory ratios as supportive markers in paediatric brucellosis

Article Title: Retrospective case–control study of haematological indices and inflammatory ratios in the diagnosis of paediatric brucellosis

Article References: Erdeniz, E. H., & Kar, Y. D. (2026). Retrospective case–control study of haematological indices and inflammatory ratios in the diagnosis of paediatric brucellosis. BMC Infectious Diseases, 26(1), Article 1737. https://doi.org/10.1186/s12879-026-14384-2

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DOI: 10.1186/s12879-026-14384-2

Keywords: paediatric brucellosis, red cell distribution width, blood count, inflammatory ratios, case–control study, diagnostic markers, plateletcrit, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, Turkey, Retrospective, case