| Abstract: | A rapid (<7-min) immunochromatographic test for immunoglobulin M (IgM) and IgG antibodies to dengue viruses was evaluated by using hospital admission and discharge sera from 124 patients. The reference laboratory diagnosis was based on the results of virus isolation, hemagglutination-inhibition assay (HAI), and enzyme immunoassay (EIA). By the standard assays, patients experienced primary dengue virus infection (n = 30), secondary dengue virus infection (n = 48), Japanese encephalitis (JE) virus infection (n = 20), or no flavivirus infection (n = 26). The rapid test demonstrated 100% sensitivity in the diagnosis of dengue virus infection and was able to distinguish between primary and secondary dengue virus infections through the separate determinations of IgM and IgG. For all patients with primary dengue virus infection a positive test for IgM to dengue virus and a negative test for IgG to dengue virus were obtained, whereas for 46 of 48 patients (96%) with secondary dengue virus infection, a positive test for IgG to dengue virus with or without a positive test for IgM to dengue virus was obtained. The remaining two patients with secondary dengue virus infection had positive IgM test results and negative IgG test results. Furthermore, the rapid test was positive for patients confirmed to be infected with different dengue virus serotypes (12 infected with dengue virus serotype 1, 4 infected with dengue virus serotype 2, 3 infected with dengue virus serotype 3, and 2 infected with dengue virus serotype 4). The specificity of the test for nonflavivirus infections was 88% (3 of 26 positive), while for JE virus infections the specificity of the test was only 50% (10 of 20). However, most patients with secondary dengue virus infection were positive for both IgM and IgG antibodies to dengue virus, while no patients with JE virus infection had this profile, so cross-reactivity was only a concern for a small proportion of patients with secondary dengue infections. The rapid test demonstrated a good correlation with the reference EIA and HAI and should be useful for the rapid diagnosis of dengue virus infections. |
