Dengue Research Group, National Institute of Virology, 20 A, Dr Ambedkar Road, Pune-411001, India.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Dengue diagnosis is based on IgM and/or genome detection, virus isolation and clinical/epidemiological findings. Serological diagnosis being non-expensive and simple, is widely applied. Currently, routine tests used to screen dengue viral infection are based on detection of dengue virus specific IgM antibodies by ELISA, lateral flow or immuno-chromatography assays. However, IgM antibodies are normally detectable from 5–6 days post onset of illness. This leaves a window period of 0–4 days post onset of illness, when the dengue infected individual is IgM negative and escapes detection. It is important that the dengue positive cases are detected even when samples are obtained early in the course of infection. A study was undertaken to investigate the use of NS1 antigen based ELISA for detection of dengue infection during the early phase of infection when the IgM antibodies are not generated. The commercially available NS1 ELISA kit (Platelia Dengue NS1 Ag assay-Pan bio) and the NIV MAC-ELISA kit were used for the detection of NS1 and Dengue specific IgM antibodies respectively. Samples (n=55) obtained during the early PODs from dengue confirmed cases were analysed. All samples were positive for viral RNA by the real time PCR assay standardized in the laboratory. NS1 antigen could be detected in 85% of the samples and IgM could be detected in 41% of the samples proving NS1 to be a more sensitive test to detect early dengue cases as compared to MAC-ELISA. Thus detection of NS1 antigen could be included as a criterion for early detection of dengue infection in the absence of viral RNA detection methods.
