Steve Halasey, CLP.
At the beginning of May, the US Centers for Disease Control and Prevention issued a health advisory to update clinicians about the use of serologic testing for Zika virus among pregnant women.
According to the agency, the advisory was necessary because its previous guidance on Zika testing for pregnant women relied, in part, on the use of an enzyme-linked immunosorbent assay (ELISA) designed to detect immunoglobulin M (IgM) antibodies produced by the body to fight Zika infection. New data suggest that in some individuals Zika virus infection can result in antibodies remaining in the body for months after infection. Consequently, the results of such serological tests may not be able to determine whether women were infected before or after they became pregnant.
Accurately estimating when a woman may have been infected is important, because birth defects have been reported in a higher proportion of fetuses or infants whose mothers were infected during the first trimester of pregnancy than in later trimesters. Among pregnant women with symptom onset or exposure during the first trimester that were limited to those with laboratory-confirmed Zika virus infection, the agency notes, 15% of completed pregnancies reported birth defects of the type seen with congenital Zika infection.
For asymptomatic pregnant women living in or frequently traveling to areas with Zika virus transmission and posted CDC Zika travel notices, the agency now recommends that healthcare providers:
- Screen pregnant women for risk of Zika exposure and symptoms of Zika. Promptly test pregnant women with nucleic acid tests if they become symptomatic during their pregnancy or if a sexual partner tests positive for Zika virus infection.
- Consider testing with a nucleic acid test at least once per trimester, unless a previous test has been positive.
- Consider testing of amniocentesis specimens with a nucleic acid test if amniocentesis is performed for other reasons.
- Counsel pregnant women each trimester on the limitations of IgM and nucleic acid testing.
- Consider IgM testing to determine baseline Zika virus IgM levels as part of preconception counseling.
CDC’s recommendations for testing symptomatic pregnant women remain unchanged. However, if a symptomatic pregnant woman has lived in or traveled to an area with a posted CDC Zika travel notice, and is positive for Zika virus via IgM testing but negative via nucleic acid testing, healthcare providers should recognize that the positive IgM result does not necessarily indicate recent infection.
Steve Halasey
Chief Editor, CLP
[email protected]
(626) 219-0199
Reference
- Prolonged IgM antibody response in people infected with Zika virus: implications for interpreting serologic testing results for pregnant women [online]. Atlanta: Health Alert Network, Centers for Disease Control and Prevention, 2016. Available at: https://emergency.cdc.gov/han/han00402.asp. Accessed May 5, 2017.
