The FDA has issued an alert to doctors and pregnant women, warning them that presumptive test results for the Zika virus have turned up unexpectedly high rates of false positives. Less than half of the samples that the ZIKV Detect test said were positive for the Zika virus were later confirmed as actually having the Zika virus in CDC tests, according to The Center for Infectious Disease Research and Policy.
The FDA is alerting physicians who care for pregnant women that the U.S. commercial testing facility, Laboratory Corporation of America (LabCorp), has reported a high number of false positive results from the ZIKV Detect test.
Since Zika confirmation tests can take a week to a month to complete, the FDA issued the alert so that health care providers and patients know about a higher likelihood of false positive results, they say.
While the FDA has not yet determined if the reported false positives are related to the ZIKV Detect test or the commercial testing facility, they say it is important to remember that “IgM tests remain useful in ruling out Zika exposure but require confirmatory testing.”
In an alert to medical professionals on December 23, the FDA urged health care providers to inform their patients that presumptive positive results need to be confirmed so that pregnant women are not making health care decisions based on incomplete or inaccurate information. They also cautioned doctors not to rely on presumptive positive Zika virus IgM test results as the sole basis for significant patient management decisions.
The FDA recommends doctors look at patient history, clinical observations, epidemiological information and results from other testing such as follow-up confirmatory testing before making a Zika diagnosis. They also remind doctors that they can request that confirmation tests be prioritized by laboratories if the patient is pregnant.
The ZIKV Detect IgM Capture ELISA test, which is manufactured by InBios International, was authorized by the FDA as the first commercially available Zika serological IgM test in August. Since then, several commercial laboratories have switched their serological Zika testing from the CDC assay that was authorized at the beginning of last year to the new commercial assay.
Both the CDC test and the ZIKV Detect test report only “presumptive positive results,” and samples have to be sent for actual confirmation of the Zika virus. In the past, most of the presumptive positive results from both tests were ultimately confirmed.
After transitioning to the ZIKV Detect test, the FDA reports that LabCorp observed higher than expected false positive results. Less than half of those presumptive positive results from the ZIKV Detect test were confirmed as positive by the CDC.
In a press release directed towards pregnant women who may have been exposed to Zika and their doctors, the FDA warned pregnant women to confirm any positive Zika test before making health decisions based on the results.
If you have been tested for exposure for the Zika virus by this test and have received a preliminary positive result, this test result should be confirmed. There is a chance that a preliminary positive test result may incorrectly show that you have been exposed to the Zika virus. If you have any questions, please contact your health care provider.
As Inquisitr has previously reported, the CDC and other health officials around the world believe that Zika infection during pregnancy can cause a birth defect of the brain called microcephaly and other severe fetal brain defects. The CDC also says that other problems have been detected among infants infected with Zika virus before birth, such as defects of the eye, hearing deficits and impaired growth.
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