Experience in the validation of a rapid test for NS1 and IgM for early diagnosis during a dengue epidemic in Colombia

Dengue has a broad spectrum of syndromic presentations, making clinical diagnosis difficult in regions where acute febrile syndrome has multiple etiologies. Rapid tests for detecting NS1 and IgM are broadly proposed for the early diagnosis of dengue; however, their implementation in primary care settings is inconsistent, and the relevance of IgM detection in this context has not been firmly established. Our study aimed to describe the experience of validating an NS1-IgM rapid test in primary care settings in Bucaramanga, Colombia, during a dengue epidemic (2018 to 2020). We tested blood samples from 568 patients with a clinical diagnosis of dengue using the Bioline Dengue Duo rapid test and RT-PCR as a reference to estimate sensitivity, specificity, and positive and negative predictive values (SE, SP, PPV, and NPV, respectively). The prevalence of infection was 32.9% (95%CI: 29.1, 36.8), whereas SE and SP were 83.4% and 72.7% for NS1 without statistical heterogeneity across disease duration. NS1s PPV and NPV were 60.0% and 89.9% at the observed prevalence. Our results show that NS1 and IgM rapid tests (POCT) are feasible in the primary care setting. The contribution of the NS1 test was indisputable, with high-performance levels far superior to those of the IgM test. The NS1+IgM combination did not offer a significant advantage over NS1 alone.