Diagnosis of dengue infection in acute phase is important for clinical care, implementing control measures, surveillance and research. Currently, dengue fever is diagnosed by means of virus isolation, reverse transcriptase PCR or IgM and IgG based ELISA. Given the limitations of all the existing diagnostic methods, there is a need for rapid, sensitive and high throughput methods for detection of dengue virus in early stages of the disease. The study was conducted with the objectives to evaluate a dengue virus NS1 antigen detection ELISA and a TaqMan based real time RT-PCR for detection of all four serotypes of dengue virus, as diagnostic tools for acute dengue virus infection. Out of 330 samples, NS1 antigen was positive in 75 cases (22.7%), IgM ELISA positive in 118 cases (35.7%) and IgG was positive in 281 cases (85.1%). Though the percentage of IgG positive samples was high, they were not considered due to their persistence lifelong and also as paired sera was not collected from the patients for confirmation of Dengue infection. Among 119 cases (group C), in 71 NS1 Ag positive cases, RT PCR positivity was 39.4%. In 103 IgM positive cases, RT PCR positivity was 20.38 %. Thus sensitivity of NS1 Ag was 97.26 % and sensitivity of multiplex RT PCR was 40.27 %, while specificity for both was 100 %. Concordance between NS1 antigen detection by ELISA and Multiplex RT-PCR was found to be 63.02 %. Both NS1 antigen detection and RNA detection was highest on day 3 of illness.NS1 antigen was detected from day 2 to day 10 of illness while RT-PCR was detected from day 2 to day 8 of illness. Concordance between NS1 antigen detection by ELISA and Multiplex RT-PCR was found to be 63.02 %. NS1 antigen detection ELISA and real time RT-PCR were found to be rapid, convenient and efficient tests for diagnosing of dengue fever in acute phase and the diagnosis could be made as early as within three days of onset of fever.

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