Shock index and modified shock index at initial clinical assessment in adults with dengue from Oaxaca, Mexico: sex-based differences in a cross-sectional study

Introduction Dengue-associated plasma leakage and compensatory hemodynamic changes may precede overt hypotension. Evidence on shock index (SI) and modified shock index (MSI) distributions and sex-based differences in adults with dengue remains limited. This study aimed to describe SI and MSI at the initial recorded clinical assessment and compare these indices between women and men. Secondary exploratory analyses examined clinical, laboratory, inflammatory, and immunonutritional variables. Methods This cross-sectional observational study included 121 adults with dengue from Oaxaca, Mexico. SI was calculated as heart rate divided by systolic blood pressure, and MSI as heart rate divided by mean arterial pressure. Continuous variables were compared using Welch’s unpaired t-test or the Mann–Whitney U test, as appropriate; categorical variables were compared using Fisher’s exact test. Analyses were descriptive and exploratory. Results Participants included 69 women and 52 men; median age was 29.0 years (IQR, 21.0–45.5). Overall median SI was 0.957 (IQR, 0.801–1.137), and mean MSI was 1.257 ± 0.290. Women had higher SI [1.000 (0.811–1.221) versus 0.889 (0.794–1.000); p = 0.0122] and MSI (1.318 ± 0.319 versus 1.176 ± 0.225), with a mean MSI difference of 0.142 (95% CI, 0.044–0.240; p = 0.0049). Women had higher heart rate, whereas blood pressure measurements did not differ significantly. The neutrophil-to-lymphocyte ratio and systemic immune-inflammation index did not differ significantly by sex. The prognostic nutritional index was lower in women [44.05 (38.43–47.30) versus 47.60 (43.14–53.25); p = 0.0007]. Discussion SI and MSI were higher in women than in men. These differences coincided with higher heart rate, whereas blood pressure measurements did not differ significantly between sexes. Because we did not assess disease severity, diagnostic performance, or longitudinal outcomes, these unadjusted findings are exploratory and require prospective validation before clinical thresholds or prognostic implications can be established.