Utility of NS1 antigen as an early serological marker in the diagnosis of dengue

Abstract

Introduction: Dengue infection is one of the most common arboviral infection in India transmitted by the aedes mosquitoes. Early diagnosis of the infection is often missed if only the antibodies are tested. In this scenario detection of the NS1 antigen has gained importance which has very high specificity and can be detected from the first day of fever. Rapid immunochromatographic tests for the detection of both NS1 antigen as well as the IgM and IgG antibodies have been extensively used in the diagnosis of dengue infection because of the ease of performing when compared to ELISA testing. The present study aims in identifying various dengue markers in the early diagnosis of dengue fever. Materials and Methods: All the suspected dengue samples obtained in the Department of Microbiology were tested by rapid immunochromatography test for the detection of NS1 and IgM/IgG antibodies. Platelet counts were detected by automated analyzer and history and duration of fever has been taken. Results: A total of 1021 samples were tested for dengue infection out of which 158(15.4%) were positive for one or more of the dengue serology markers. Out of the 158, 85(53.79%) were positive only for NS1 antigen indicating the infection in the early stage, 60(37.97%) samples showed only IgM dengue antibodies and 6(3.79%) samples showed only IgG antibodies. Two serological markers are seen in 7 samples, out of which 4(2.53%) samples were positive for NS1+ IgM antibodies and the remaining 3(1.89%) samples for IgM+IgG antibodies. Majority of the cases were in the age group of 16-30 years and males were predominantly affected when compared to females. Decreased platelet count was observed in 62 out of 158 cases (39.2%). Maximum NS1 positivity was observed form 2nd to 7th day of fever where as IgM positivity was maximum between 7th to 9th day. Conclusion: Early diagnosis of dengue infection is warranted by the detection of NS1 antigen. Detection of NS1 antigen along with the IgM/IgG will ide