Serological and Immunological Markers in Dengue Fever: A Retrospective ELISA-Based Pilot Study from Trinidad and Tobago.

Background: Dengue fever remains a major mosquito-borne viral disease in tropical and subtropical regions and continues to represent an important public health challenge in the Caribbean. Despite endemic transmission in Trinidad and Tobago, limited laboratory-based studies have evaluated serological markers associated with recent dengue infection. Objective: To evaluate serological and immunological markers associated with recent dengue virus infection through the detection of anti-dengue virus immunoglobulin M (IgM) antibodies in serum samples obtained from Trinidad and Tobago using an enzyme-linked immunosorbent assay (ELISA). Methods: Anti-dengue virus IgM antibodies were detected using a commercial enzyme-linked immunosorbent assay (ELISA). Results were classified as positive, borderline or negative according to manufacturer-recommended criteria. Descriptive statistical analysis was performed to determine seroprevalence in anonymized serum samples. Results: A total of 161 serum samples were analyzed. Twenty samples (12.4%) demonstrated positive anti-dengue IgM reactivity, while 29 samples (18.0%) showed borderline reactivity and 112 samples (69.6%) were negative. Under the conservative analytical approach, the estimated dengue IgM seroprevalence was 12.4% (20/161; 95% CI: 7.7-18.6%). Conclusions: The estimated seroprevalence of dengue IgM in this pilot study was highly dependent on the analytical treatment of borderline ELISA results. Conservative classification provided the most cautious and reproducible estimate of recent dengue infection, while liberal interpretation substantially increased the apparent disease burden. Early viral replication triggers inflammation that progresses to cytokine-driven vascular damage, while cross-reactive humoral responses and host factors ultimately shape dengue severity. Ultimately, understanding the drivers of IgM cross-reactivity is essential for accurate dengue surveillance, outbreak detection, and clinical decision-making.