Comparison of two rapid diagnostic assays for detection of immunoglobulin M antibodies to dengue virus

Two easy-to-use commercial diagnostic assays, a dipstick enzyme-linked immu nosorbent assay (ELISA) (Integrated Diagnostics, Baltimore, Md,) and an imm unochromatographic card assay (PanBio, Brisbane, Australia) were evaluated for detection of immunoglobulin M (IgM) antibody to dengue virus with an in -house IgM antibody capture microplate ELISA as a reference assay. The dips tick ELISA was based on the indirect-ELISA format using dengue 2 virus as t he only antigen and enzyme-labeled goat anti-human IgM antibody as the dete ctor. The total assay time was 75 min. The immunochromatographic card assay was based on the antibody capture format and separately measured both anti -dengue virus IgM and IgG in the same test. Colloidal-gold-labeled anti-den gue virus monoclonal antibody bound with dengue virus 1 to 4 antigen cockta il was the detector, and anti-human IgM and IgG were the capture antibodies . The total assay time,vas < 10 min. Sera from 164 individuals classified a s either anti-dengue virus IgM positive (94) or anti-dengue virus IgM negat ive (70) in the reference microplate ELISA with a dengue virus 1 to 4 antig en cocktail were tested in the two commercial assays. The dipstick ELISA mi ssed 7 of 94 positive samples, for a sensitivity of 92.6%, while the immuno chromatographic card assay missed two positive samples, for a sensitivity o f 97.9%. Of the 70 negative samples, four were false positive by the dipsti ck ELISA and two were false positive in the immunochromatographic card assa y, resulting in specificities of 94.3 and 97.1%, respectively. Both commerc ial assays provide sensitive and specific detection of anti-dengue virus Ig M antibody and could prove useful in settings where the microplate ELISA is impractical.