Simultaneous Detection of Dengue NS1 Antigen, IgM plus IgG and Platelet Enumeration during an Outbreak

Objectives:During 2010, there was an increase in dengue virus infections in New Delhi, India compared to 2009. This study was conducted at Sant Parmanand Hospital during this outbreak to determine the utility of a ‘Dengue Package’, comprising simultaneous detection of dengue non-structural protein 1 (NS1), antidengue IgM, anti-dengue IgG and platelet enumeration for early diagnosis, better case management and faster public health response. Methods: Blood samples were tested for Dengue NS1, IgM and IgG using the singlestep immunochromatigrahic One-step dengue NS1 Ag and IgG/IgM test, while platelets were enumerated with automatic analysers yielding results within 1–2 hours. Results: Of the 1,886 patients screened with the ‘Dengue Package’, 678 and 1208 were NS1-positive and -negative respectively, in different combinations. In 394 cases, NS1 was exclusively positive while 29 were also IgG positive. In 942 cases NS1, IgM and IgG were negative (triple negative). The platelet counts in the NS1 positives were lower than the NS1 negatives, mean and standard deviation (SD) 116.8±70.2 x 109/L: 95% confidence interval (CI) 66.6–74.1 and 167.2±94.0 x 109/L, P<0.0001. Platelet counts were <20 x 109/L in 20 NS1 antigen-positives and 42 NS1 antigen-negatives. Conclusion: During the 2010 outbreak, swift availability of the ‘Dengue Package’ assisted patient management, platelet transfusions, implementation of anti-vector measures and public health notifications. Testing for NS1 assisted the diagnosis of an additional 22.4% cases; of these 394 had evidence of primary infection and 29 of secondary infection. The ‘Dengue Package’ was useful in tackling the rise in suspected cases.