How is serologic testing used in the workup of Zika virus infection?

Updated: Dec 11, 2018
  • Author: Bhagyashri D Navalkele, MD, MBBS; Chief Editor: Michael Stuart Bronze, MD  more...
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Answer

Prompt diagnosis and laboratory confirmation of Zika virus infection is challenging.

Serologic Testing

Zika virus infection is diagnosed based on detection and isolation of Zika virus RNA from serum using reverse-transcriptase polymerase chain reaction (RT-PCR). The highest sensitivity of PCR testing is during the initial week of illness, which is characterized by high viremia. After the initial week of illness, serological testing for virus-specific immunoglobin M (IgM) and neutralizing antibodies against Zika virus infection can be performed using enzyme-linked immunosorbent assay (ELISA). [16] The utility of this test is limited owing to cross-reactivity with other flaviviruses (dengue and yellow fever). Antibodies directed toward individual flaviviruses can be measured using plaque reduction neutralization tests (PRNTs) to facilitate accurate diagnosis of primary flavivirus infection.

The CDC has issued interim guidance on Zika virus antibody testing and interpretation, as follows: [23]

Serum IgM testing should be performed if real-time RT-PCR (rRT-PCR) results are negative, regardless of when the specimen was collected.

A 4-fold higher titer based on plaque reduction neutralization test (PRNT) results might not differentiate anti-Zika virus antibodies from cross-reacting antibodies in all persons with previous infection or vaccination against a related flavivirus.

If IgM testing is positive for Zika or dengue virus or returns equivocal results, the following PRNT interpretations apply:

  • A PRNT titer >10 indicates evidence of infection with that specific flavivirus when the PRNT to the other flavivirus(es) tested is <10.
  • A PRNT titer <10 to a specific flavivirus indicates an absence of infection with that virus.
  • A positive PRNT result (>10 to multiple flaviviruses) indicates evidence of recent flaviviral infection.

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