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Dengue diagnostic process. Image courtesy CDC.

Dengue Virus Laboratory Diagnosis

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.
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 immunosorbant 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:
  2. IgG ELISA
  3. Plaque reduction and neutralization test (PRNT)

Immunological response to dengue infection. Image courtesy CDC.