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Types of Zika Virus Tests

Summary

  • Key Points: CDC and several state and local health departments are testing for Zika virus. Different diagnostic tests are available to help determine if a person is infected with Zika virus disease. Healthcare providers should contact their state or local health department to facilitate testing.

If you have a symptomatic patient who lives in or recently traveled to an area with Zika, he or she may have been infected with other mosquito-borne viruses like dengue or chikungunya that often circulate in the same geographic regions and present with a similar clinical illness.

The FDA has issued Emergency Use Authorization (EUA) for several diagnostic tools for Zika virus, including the Trioplex Real-Time RT-PCR (rRT-PCR) assay and the Zika MAC-ELISA, which are being distributed to qualified laboratories.

Molecular Test for Zika Virus

For symptomatic persons with Zika virus infection, Zika virus RNA can sometimes be detected early in the course of illness. RNA NAT (nucleic acid testing) should be performed on serum collected during the first two weeks after symptom onset. RNA NAT testing should also be conducted on urine samples collected less than 14 days after symptom onset. Urine should always be collected with a patient-matched serum specimen. A positive RNA NAT result on any sample confirms Zika virus infection and no additional testing is indicated. A negative RNA NAT result does not exclude Zika virus infection and serum should be analyzed by IgM antibody (serological) testing.

For asymptomatic pregnant women who have traveled to areas with active ZIKV transmission, RNA NAT testing is recommended on serum and urine within 2 weeks of the date of last possible exposure. RNA NAT testing is also indicated for pregnant women who present for care ≥ 2 weeks after exposure and have been found to be IgM positive. In areas with active ZIKV transmission, asymptomatic pregnant women should undergo IgM testing as part of routine obstetric care in the 1st and 2nd trimester. Reflex RNA NAT testing is included as a subsequent test for women who are IgM positive.

Trioplex Real-time RT-PCR Assay

The Trioplex rRT-PCR is a laboratory test designed to detect Zika virus, dengue virus, and chikungunya virus RNA. The Food and Drug Administration (FDA) has not cleared or approved this test. However, FDA has authorized the use of this test under an Emergency Use Authorization (EUA). More information on the Trioplex rRT-PCR assay can be found on the Lab Guidance webpage.

Zika Virus - Trioplex Real-Time RT-PCR Assay Testing Instructions:

See Understanding Zika Virus Test Results for Healthcare Provider and Patient Fact Sheets on the Trioplex Real-Time RT-PCR Assay.

Serologic Test for Zika Virus

Zika virus-specific IgM and neutralizing antibodies typically develop toward the end of the first week of illness. IgM levels are variable, but generally are positive starting near day four post onset of symptoms and continuing for 12 weeks Therefore, if RNA NAT is negative on serum and urine, serum IgM antibody testing for Zika, dengue, and chikungunya virus infections should be performed. In addition, serum samples collected >=14 days after symptom onset, with no earlier samples collected, should be tested for anti-Zika virus, anti-dengue virus, and anti-chikungunya virus IgM antibodies.

Zika MAC-ELISA

The Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (Zika MAC-ELISA) is used for the qualitative detection of Zika virus IgM antibodies in serum or cerebrospinal fluid; however, due to cross-reaction with other flaviviruses and possible nonspecific reactivity, results may be difficult to interpret. Consequently, presumed positive, equivocal, or inconclusive tests must be forwarded for confirmation by plaque-reduction neutralization testing (PRNT). PRNT is performed by CDC or a CDC-designated confirmatory testing laboratory to confirm presumed positive, equivocal, or inconclusive IgM results.

See Understanding Zika Virus Test Results for Healthcare Provider and Patient Fact Sheets on the MAC-ELISA Test

Zika virus-specific IgM testing should be performed on asymptomatic pregnant women that have traveled to an area with Zika within 2-12 weeks after travel or who had sexual contact with a man confirmed to have Zika virus infection. In areas with active ZIKV transmission, asymptomatic pregnant women should undergo IgM testing as part of routine obstetric care in the 1st and 2nd trimester.

Presumed positive, equivocal, or inconclusive IgM results must be forwarded for confirmation by PRNT.

Plaque Reduction Neutralization Test (PRNT)

Samples with presumptive positive, equivocal, or inconclusive IgM test results must be forwarded for confirmation by PRNT.

For more information on interpretation of diagnostic test results, see Interim Guidance for Interpretation of Zika Virus Antibody Test Results.

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