Finding the right tests…
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Finding the right tests…
ELISA
Dengue ELISA NS1 finds a piece of the dengue virus itself, its NS1 protein, rather than an antibody your body makes in response, which is why it can turn positive earlier than either dengue antibody test, often from day 1 of fever. Run as a lab ELISA rather than a rapid card, it works best in the first week of illness, before the protein clears from your blood. Doctors order it as the front-line dengue test for fresh fever in a dengue-prone season, usually alongside IgM, because NS1 tends to fade in accuracy after about a week, especially in someone who has had dengue before.
This ELISA test looks for the NS1 viral protein itself in a blood sample, read on a laboratory plate reader rather than a rapid strip, and reported as reactive or non-reactive. It performs best when drawn in the first week of fever; a non-reactive result later in the illness, or in someone with past dengue, does not rule out a current infection. Your doctor typically reads it together with IgM and the day of illness you're on.
NS1 is a viral protein dengue makes and releases into your blood during active infection, not an antibody, so it shows up before your immune system has had time to respond. In primary dengue infections it has been picked up from day 1 of illness, with sensitivity around 89% to 91% when samples are taken in the first week, then it declines and is usually undetectable by around day 9 in a first infection, or a little earlier, around day 6, in someone who has had dengue before.
That window is the whole point of ordering NS1: it fills the gap before IgM and IgG antibodies build up, so a person tested on day 1 or 2 of fever, before antibodies would show anything, can still get an answer. Because NS1 clears faster in secondary infections, thanks to a quicker antibody response mopping it up, a negative NS1 in someone with a strong dengue-like illness and a prior dengue history does not rule dengue out, and your doctor may add IgM or a repeat test.
The ELISA format reads the result on a lab plate rather than a rapid strip, which typically gives a more precise, lab-verified answer than a bedside card test, though it takes longer to process.
It has been picked up from as early as day 1 of fever in studies of first-time dengue infections, with good sensitivity through the first week of illness.
Not completely, especially later in the illness or in someone who has had dengue before, since NS1 clears from the blood faster in repeat infections. Your doctor may add IgM or repeat testing if dengue is still suspected.
A quicker antibody response in someone previously infected clears the NS1 protein from the blood sooner, sometimes by around day 6 of illness instead of closer to day 9.
No. NS1 is a piece of the virus itself, a protein it releases into the blood, not an antibody your immune system makes. That's why it can turn positive before any antibody test would.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
This version is processed as an ELISA test on a laboratory plate reader instead of a bedside strip, which typically gives a more precise, quantifiable result, though turnaround is usually a little longer.
Many doctors do order both together in the first week of fever, since NS1 catches the earliest window and IgM helps once NS1 starts to decline. Ask your doctor what combination fits your situation.
Ask your doctor or the centre about preparation; a routine blood draw for NS1 typically needs no special fasting, but confirm ahead of your visit.