Potential for falsely low blood lead test results from LeadCare® analyzers
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Potential for falsely low blood lead test results from LeadCare® analyzers

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      May 17, 2017 0900 ET (9:00 AM ET)


      In July 2016, CDC issued Interim Guidance for Health Care Providers Caring for Pregnant Women with Possible Zika Virus Exposure – United States, July 2016 (https://www.cdc.gov/mmwr/volumes/65/wr/mm6529e1.htm) that includes Zika virus immunoglobulin M (IgM) testing of pregnant women. However, some flavivirus infections can result in prolonged IgM responses (>12 weeks) that make it difficult to determine the timing of infection, especially in testing of asymptomatic people. Emerging epidemiologic and laboratory data indicate that Zika virus IgM can persist beyond 12 weeks in a subset of infected people. Therefore, detection of IgM may not always indicate a recent infection. Although IgM persistence could affect IgM test interpretation for all infected people, it would have the greatest effect on clinical management of pregnant women with a history of living in or traveling to areas with Zika virus transmission. Pregnant women who test positive for IgM antibody may have been infected with Zika virus and developed an IgM response before conception.

      For asymptomatic pregnant women with a history of living in or traveling to areas with Zika virus transmission, Zika virus nucleic acid test (NAT) testing at least once per trimester is recommended, in addition to IgM testing as previously recommended. If positive, this may provide a more definitive diagnosis of recent Zika infection. However, a negative NAT does not rule out recent infection because viral ribonucleic acid (RNA) declines over time. Other diagnostic methods, such as NAT testing of amniocentesis specimens or serial ultrasounds, may provide additional information to help determine whether the IgM test results suggest a recent infection. Providers should counsel women on the limitations of all tests. In addition, providers may wish to consider IgM testing as part of pre-conception counseling to establish baseline IgM results before pregnancy; however, preconception negative IgM results might have limited value for women at ongoing risk of Zika infection. NAT testing should be performed for any pregnant woman who becomes symptomatic or who has a sexual partner who tests positive for Zika virus infection.

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