Molecular methods
Reverse transcription-polymerase chain reaction (RT-PCR) can detect dengue virus in the blood during the first five days of symptoms with a sensitivity of 80-90% and a specificity of 95%. CDC developed the test as a real-time RT-PCR (rRT-PCR) assay that detects serotypes 1-4.
Serology
If a patient has not received a vaccine for yellow fever or been infected with Japanese encephalitis virus or tick-borne encephalitis, IgM will be detectable in 50% of cases by three to five days after the onset of symptoms, 80% after day five, and 99% by day ten. IgM will then decline to undetectable after two to three months. The recommended serological test is an IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA). Limitations include that a positive IgM may be detecting an infection three months after the illness and there is cross-reactivity with antibodies to West Nile virus, Yellow Fever virus, Japanese encephalitis virus, and St. Louis encephalitis. Positive patient serum can be confirmed by plaque-reducing neutralization test for antibodies.
IgG is detectable by ELISA at the end of week one until several months or years later. A titer of 1:1,280 is considered highly suspect by the World Health Organization (WHO). Acute specimens drawn by day five and a convalescent specimen at day ten or later are required to demonstrate a four-fold rise in titer for a definitive diagnosis by serology.
Dengue tests for nonstructural 1 (NS1) glycoprotein antigen and antibody tests have shown cross-reactivity with other flaviviruses.
Classical testing algorithms of dengue if molecular tests are negative:
- MAC ELISA
- IgG ELISA
- Plaque reduction and neutralization test (PRNT)
