Clinical implications of Widal false positivity among children presenting with dengue infection: a comparative cohort study

Objective: Dengue fever often coincides with other endemic infections such as typhoid, leading to diagnostic overlap. The Widal test, though frequently used for typhoid diagnosis, may show false positivity in dengue cases due to nonspecific immune activation. However, the clinical implications of Widal test results in children with confirmed dengue without typhoid co-infection remain unclear. Patients and Methods: This prospective comparative cohort study was conducted at a tertiary care pediatric hospital in North India between June 2022 and November 2023. Children aged 1 month to 18 years with confirmed dengue infection were enrolled. Widal positivity was defined as TO (Typhi O; somatic antigen of Salmonella Typhi) or TH (Typhi H; flagellar antigen of Salmonella Typhi) titers > 1:80. Blood cultures were performed in all patients to exclude typhoid fever. Baseline clinical parameters, hematological and biochemical markers, and clinical outcomes were compared between Widal-positive and Widal-negative groups. Results: Out of 152 enrolled children with confirmed dengue, 60 (39.5%) were Widal-positive and 92 (60.5%) Widal-negative. Children with Widal-negative dengue had significantly higher blood urea levels (p=0.02), prolonged prothrombin time (p=0.01), and greater need for fluid boluses (17.4% vs. 1.7%, p=0.003), suggesting a more severe disease profile, although these findings represent exploratory outcomes and should be interpreted as hypothesis-generating. In contrast, Widal-positive children had a longer duration of fever (p<0.001) and a higher frequency of vomiting, but did not show increased complication rates. Conclusions: In this exploratory analysis, Widal negativity in children with dengue infection appears to be associated with more severe clinical manifestations. While Widal positivity is often disregarded as nonspecific, its absence may carry prognostic significance. As severe dengue was an exploratory outcome, these findings warrant further investigation and should be considered hypothesis-generating.