Early dengue diagnosis: Role of rapid NS1 antigen, NS1 early ELISA, and PCR assay

Abstract

Context: Early and accurate dengue diagnosis is important for disease surveillance, and also to start effective control measures in endemic countries. Aims: In this study, we evaluated the performance of three techniques available for early dengue diagnosis, viz., rapid nonstructural 1 (NS1) antigen test, NS1 early enzyme-linked immunosorbent assay (ELISA) test, and reverse transcription polymerase chain reaction (RT-PCR) test. Settings and Design: Retrospective analytical study. Materials and Methods: Performance of three different techniques, viz., rapid NS1 antigen, NS1 early ELISA, and RT-PCR on serum samples of suspected dengue cases. Statistical Analysis Used: Sensitivity, specificity, negative predictive value, and positive predictive value calculated for rapid test and ELISA test, keeping PCR as the gold standard Results: Amongst 155 samples received from clinically-suspected dengue cases within 1-9 days of fever, 56 samples were received during 1-3 days, 52 samples were received during 4-6 days, and 47 samples were received during 7-9 days. Of these 155 samples, 38 (24.5%) were positive by rapid NS1 antigen, 47 (30.3%) by NS1 ELISA, and 54 (34.8%) by reverse transcriptase polymerase chain reaction (RT-PCR). Rapid NS1 antigen and NS1 ELISA showed the highest positivity on days 1-3, while highest positivity for PCR was on days 4-6. The sensitivity and specificity of NS1 ELISA were 66.6% and 89.1%, while sensitivity and specificity of rapid NS1 antigen were 55.5% and 92%, respectively. Conclusions: With high mortality and morbidity associated with dengue, it is imperative to diagnose the disease during the early phase. All three assay formats are helpful in early diagnosis and to provide information of dengue cases in time.