Comparison of NS1 antigen detection ELISA, real time RT-PCR and virus isolation for rapid diagnosis of dengue infection in acute phase.

BACKGROUND & OBJECTIVES 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. METHODS The acute phase serum samples of patients (n=153) presenting with dengue fever were subjected to NS1 antigen detection and real time RT-PCR. The results were compared to those of virus isolation in the C6/36 cell lines (n=55). RESULTS The efficiency, sensitivity, specificity, positive and negative predictive values of NS1 Ag detection ELISA were 83.6, 73.5, 100, 100 and 70% respectively while for real time RT-PCR these were 87.3, 79.4, 100, 100 and 75% respectively. Maximum sensitivity of NS1 antigen detection ELISA was seen in two days of fever and that of real time RT-PCR in three days of fever. INTERPRETATION & CONCLUSION 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.