Current status of dengue diagnosis at the center for disease control, Taiwan

A national-level diagnostic laboratory has been set up in Taiwan for routine diagnosis of reported cases of dengue fever (DF)/dengue haemorrhagic fever (DHF), Japanese encephalitis (JE) and yellow fever (YF). The facilities include serological diagnosis, virus isolation by cell culture, molecular diagnosis and molecular tools for epidemiological investigations. To detect and differentiate dengue, JE and YF virus infections, a differential diagnostic system has been developed. For acute-phase sera, virus isolation by cell culture and real-time one-step reverse transcription-polymerase chain reaction (RT-PCR) has been established. For all of the serum samples reported, serological diagnosis of specific antibodies based on envelope and membrane (E/M)-specific capture IgM and IgG enzyme-linked immunosorbent assay (ELISA) are performed. In this report, a case study from Taiwan has been presented with the analysis of 959 serum samples (including some paired sera) collected between day 1-30 of illness from 799 confirmed dengue cases reported in 2002. The results demonstrated that 94.5% of acute-phase serum samples of confirmed dengue cases could be identified as positive or probable with the combined use of real-time one-step RT-PCR and E/M-specific capture IgM and IgG ELISA. Furthermore, a nonstructural protein NS1 serotype-specific indirect IgG ELISA has been developed and used to analyse dengue NS1-specific IgG antibodies. Both E/M-specific capture IgM and IgG ELISA and the NS1 serotype-specific indirect IgG ELISA have been used to detect and differentiate primary and secondary dengue virus infections. In addition, the NS1 serotype-specific indirect IgG ELISA has the potential of replacing the plaque-reduction neutralization test (PRNT) and is being used for a large-scale seroepidemiological study.