Dengue NS1 antigen detection: A useful tool in early diagnosis of dengue virus infection

Purpose: This study was undertaken to evaluate the efficacy of NS1 antigen (Ag) assay as an early marker for dengue virus (DV) infection.
Materials and Methods: Group I evaluated the performance of NS1 antigen (Ag) assay in comparison to MAC-ELISA and their detection rate when performed together in a single sample. Six hundred acute/early convalescent sera were screened by both the assays. Group II evaluated the efficacy of a single assay in 30 acute phase sera of paediatric OPD patients screened only by NS1 Ag assay. Group III evaluated the specificity of NS1 assay in comparison to MAC-ELISA on 40 samples included as controls.
Results: In Group I, 140 (23.3%) and 235 (39.1%) samples were positive by NS1 assay and MAC-ELISA respectively. The detection rate increased to 320 (53.3%) when both the assays were used together on a single sample. NS1 Ag positivity varied from 71.42% to 28.4% in acute and early convalescent sera, conversely IgM detection rate was 93.61% and 6.38% in early convalescent and acute phase sera respectively (P < 0.0001). In Group II, 66.66% (20) samples were positive by NS1 assay. All the samples in Group III were negative showing 100% specificity of both the assays.
Conclusion: NS1 Ag assay holds promise in early diagnosis of dengue infection. When used in combination with MAC-ELISA on a single sample it significantly improves the diagnostic algorithm without the requirement of paired sera.

Keywords
Acute phase sera, dengue, laboratory diagnosis, MAC-ELISA, NS1 antigen assay