FDA Warns Against Relying on Zika Test Results

CDC confirmed less than half of the presumptive positive results captured by LabCorp through the ZIKV Detect test
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(Zika News)

In August 2016, the Food and Drug Administration (FDA) authorized the ZIKV Detect IgM Capture ELISA as the first commercially available Zika serological IgM test.

Since then, several commercial laboratories have started migrating their testing from the Centers for Disease and Control (CDC) assay, to the new commercial assay.

The CDC test and the ZIKV Detect test both report only presumptive positive results.

Samples are then sent for confirmation. Past performance characteristics indicate most of the presumptive positive results from both tests have been ultimately confirmed.

After transitioning to the ZIKV Detect test, LabCorp, a commercial laboratory, observed higher than expected false positive results.

The CDC confirmed less than half of those presumptive positive results captured by LabCorp through the ZIKV Detect test.

Because confirmation tests may take a week to a month to complete, the FDA is issuing this alert so that health care providers and patients know about a higher likelihood of false positive results.

The FDA said in a press release, ‘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.”

Additionally, the FDA announced clinicians running a preliminary Zika virus test through LabCorp for their pregnant patients shouldn't jump to conclusions about the results, especially in light of a higher-than-expected rate of false positives.

Because the Zika test in question — called ZIKV Detect — is presumptive, it should always be confirmed by the CDC or by qualified laboratories.

Therefore, clinicians should not rely on ZIKV Detect results as the only basis of "significant patient management decisions," the FDA said in a MedWatch safety communication.

Likewise, pregnant women should not make healthcare decisions on the basis of partial information.

Zika is spread mostly by the bite of an infected Aedes species mosquito (Ae. aegypti and Ae. albopictus). These mosquitoes bite during the day and night. Zika can be passed from a pregnant woman to her fetus. Infection during pregnancy can cause certain birth defects. There is no vaccine or medicine for Zika.

The FDA is currently working with CDC, LabCorp, and InBios to identify the root cause of the problem. The FDA will continue to monitor the situation to assure the safety and effectiveness of these tests, and will keep the public informed if significant new information becomes available.

Here are the current CDC Zika test recommendations.

To report any problems with ZIKV Detect, contact MedWatch, the FDA's safety information and adverse event reporting program, by telephone at 1-800-FDA-1088; by fax at 1-800-FDA-0178; online at https://www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm; or by mail to MedWatch, 5600 Fishers Lane, Rockville, Maryland 20852-9787.