Systemic inflammation and malaria co-infection in irritable bowel syndrome: a cross-sectional study of 142 Yemeni patients

OBJECTIVE: To determine the prevalence of malaria co-infection among patients with irritable bowel syndrome (IBS) in Yemen and to evaluate the association of systemic inflammatory biomarkers (neutrophil-to-lymphocyte ratio (NLR), mean platelet volume (MPV) and platelet-to-lymphocyte ratio (PLR)) with this co-infection. DESIGN: Multicentre, cross-sectional observational study conducted between April and December 2024. SETTING: Primary and secondary healthcare facilities across 21 governorates in Yemen. PARTICIPANTS: 142 consecutive adult patients (aged 18-70 years) diagnosed with IBS according to the Rome IV criteria. OUTCOME MEASURES: The primary outcome was the prevalence of malaria infection, confirmed by a rapid diagnostic test . Secondary outcomes included differences in NLR, MPV and PLR between groups, assessed using independent t-tests, and the diagnostic performance of these biomarkers evaluated by receiver operating characteristic curve analysis with AUC calculation. Multivariate binary logistic regression was used to identify independent predictors of malaria co-infection, adjusting for potential confounders. RESULTS: The mean age was 42.3 years (SD 11.7) with an equal gender distribution. The prevalence of malaria co-infection was 45.1% (64/142). Patients with malaria positivity had significantly higher NLR (mean difference 0.56, 95% CI 0.40 to 0.72; p<0.001) and PLR (mean difference 22.6, 95% CI 17.8 to 27.4; p<0.001) and lower MPV (mean difference -0.60 fL, 95% CI -0.77 to -0.43; p<0.001) compared with malaria-negative patients. In adjusted logistic regression, higher NLR (adjusted OR 3.21, 95% CI 1.89 to 5.45) and PLR (adjusted OR per 10-unit increase 4.02, 95% CI 2.24 to 7.18) were independently associated with malaria positivity. CONCLUSIONS: Nearly half of the Yemeni patients with IBS in this study had malaria co-infection, with the highest burden in diarrhoea-predominant and mixed subtypes. Elevated NLR and PLR were strongly associated with co-infection, suggesting these readily available biomarkers could aid targeted screening in resource-limited, endemic settings.