Early detection of complications significantly reduces mortality and morbidity associated with dengue. We set out to determine whether the rapid NS1 antigen test could be used as a point-of-care test to predict severe disease.
186 adult patients with confirmed dengue were enrolled on days 3-8 of illness. Clinical and laboratory parameters were recorded during the course of the disease and NS1 antigen levels were determined using the Panbio Dengue Early Dengue ELISA (Panbio, Australia) and an NS1 Antigen Rapid Detection Kit (SD Bioline, South Korea). South).
What is the test?
- NS1 tests detect the nonstructural protein NS1 from the dengue virus. This protein is secreted into the blood during dengue infection.
- The NS1 tests have been developed for use in serum. Most of these tests use synthetically labelled antibodies to detect the Dengue NS1 protein.
How should it be used and at what time during infection?
- NS1 is detectable during the acute phase of dengue virus infections. NS1 tests can be as sensitive as molecular tests during the first 0 to 7 days of symptoms. After day 7, NS1 testing is not recommended.
- A positive NS1 test result is indicative of dengue infection but does not provide serotype information. It is not necessary to know the serotype of the infectious virus for patient care; however, if serotype information is needed for surveillance purposes, the sample should be analyzed by NAT.
- Although studies show that NS1 can be found in whole blood or plasma, most NS1 tests have been developed and evaluated in serum samples. While tests combined with a test for NS1 and IgM antibodies can generally provide a diagnostic result during the first 1-7 days of illness, a second sample should be obtained from the convalescent phase and analyzed for IgM when both tests antigen and antibody are negative.
Interpretation of results
- A positive NS1 test result confirms dengue virus infection without providing serotype information.
- A negative NS1 test result does not rule out infection. People with negative NS1 results should be tested for the presence of IgM antibodies to dengue to determine possible recent exposure to dengue.
Dengue NS1 tests are available as commercial diagnostic kits; The US Food and Drug Administration authorizes a limited number. Some commercial and public health laboratories use these tests.
59.1% of patients presented to the hospital on day 5-6 of illness when NS1 antigen positivity was significantly associated (p = 0.008) with severe dengue (odds ratio 3.0, 95% CI: 1.39 to 6.47) and NS1 antigen levels were significantly higher (p = 0.03) in those who developed shock. Serum NS1 antigen levels were significantly (p <0.0001) and inversely correlated with total white blood cell and lymphocyte counts. The bedside NS1 test showed a sensitivity (97.4%) and specificity (93.7%) comparable to the laboratory NS1 test in our setting and cohort.
NS1 antigen positivity is associated with an increased risk of developing severe dengue, especially when positive after disease day 5 in our cohort, and although further validation studies are required, the test can therefore potentially be used. as a test at the point of care to the bedside as a warning. sign of severe dengue.