Rationale for Timing of Diagnostic Testing

Events are essentially the same, but not identical, for both a primary and secondary DENV infection.

At or shortly before the onset of fever and for about 5 days
DENV is present in the circulation and can be detected using molecular diagnostic tests such as RT-PCR.
NS1 antigen is detectable in serum and parallels the detection of DENV by RT-PCR, though it might be detectable for a few days longer
Later in the febrile phase (~ day 3 or 4 after the onset of fever):
IgM anti-DENV becomes detectable and remains detectable for several months after the DENV infection.
During the recovery phase in a patient with their first (primary) DENV infection
IgG anti-DENV appears for first time and remains detectable for life.
At the time of illness onset in a patient with a 2nd, 3rd, or 4th (secondary) DENV infection
IgG anti-DENV is present and therefore this test is not useful in making a diagnosis. However, this test is included in a number of dengue diagnostic testing packages offered by laboratories.

The graphic regarding the virologic and immunologic events that occur during the course of dengue is for illustration purposes only and are not based on actual data.

Legend

DENV-reactive IgG

DENV-reactive IgM

Dengue viral protein, NS1

Rationale for Timing of Diagnostic Testing

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