Background: Dengue fever, caused by one of four antigenically distinct serotypes of the Flaviviridae family, remains a formidable public health challenge across tropical and subtropical regions. The clinical spectrum ranges from self-limiting febrile illness to life-threatening complications, including dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS).

Objective: This cross-sectional analytical study investigated the interrelationship between key haematological parameters — platelet count, hematocrit, and total leukocyte count — and serological markers, specifically NS1 antigen and dengue-specific IgM antibodies.

Methods: A total of 342 dengue seropositive patients aged 18–55 years were enrolled at Santosh Medical College and Hospital, Ghaziabad, India, over six months (January–June 2025). Data on demographic profiles, clinical presentation, and laboratory parameters were systematically collected. Spearman's rank correlation coefficient (ρ) was applied to assess bivariate relationships among continuous variables.

Results: The cohort comprised 220 males (64.3%) and 122 females (35.6%), with a mean age of 39.49 ± 11.11 years. Spearman's rank correlation analysis revealed a weak positive correlation between platelet count and hematocrit (ρ = 0.127, p = 0.019) and a weak negative correlation between NS1 antigen positivity and hematocrit (ρ = −0.168, p = 0.002). No significant correlations were observed between NS1 antigen and platelet count or leukocyte count, nor between IgM antibody and any haematological parameter (p > 0.05). These findings suggest that thrombocytopenia in dengue patients occurs independently of serological markers.

Conclusion: The integration of haematological and serological parameters offers clinically meaningful insights for early dengue diagnosis and severity prediction. The inverse correlation between NS1 antigen levels and hematocrit, alongside significant thrombocytopenia, underscores the need for a multiparametric diagnostic approach in resource-limited endemic settings.