Photo by Jeremy L. Grisham
The US Food and Drug Administration (FDA) has issued an Emergency Use Authorization (EUA) for a laboratory test used to detect the Zika virus.
The test, which was developed by the Centers for Disease Control and Prevention (CDC), is called the Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (Zika MAC-ELISA).
It will be distributed to certain laboratories in the US and abroad over the next 2 weeks.
The test will not be available in US hospitals or other primary care settings.
The Zika MAC-ELISA test can detect human immunoglobulin M (IgM) antibodies to the Zika virus. These antibodies appear in the blood of an infected person 4 to 5 days after the start of the illness, and they remain in the blood for about 12 weeks.
The Zika MAC-ELISA test is intended for use in sera or cerebrospinal fluid when submitted with a patient-matched serum sample from individuals meeting CDC Zika clinical and epidemiological criteria for testing. This includes people with a history of symptoms associated with Zika and/or people who have recently traveled to an area that has active Zika transmission.
Results of Zika MAC-ELISA tests require careful interpretation. The test can give false-positive results when someone has been infected with a virus closely related to Zika (such as dengue virus).
When positive or inconclusive results occur, additional testing (plaque reduction neutralization test) to confirm the presence of antibodies to Zika virus will be performed by the CDC or a CDC-authorized laboratory.
Moreover, a negative test result does not necessarily mean a person has not been infected with Zika virus. If a sample is collected just after a person becomes ill, there may not be enough IgM antibodies for the test to measure, resulting in a false-negative.
Similarly, if the sample was collected more than 12 weeks after illness, it is possible that the body has successfully fought the virus and IgM antibody levels have dropped below the detectable limit.
The CDC will begin distributing the Zika MAC-ELISA test over the next 2 weeks to qualified laboratories in the Laboratory Response Network, an integrated network of domestic and international laboratories that can respond to public health emergencies.
About the EUA
An EUA allows the use of unapproved medical products or unapproved uses of approved medical products in an emergency. The products must be used to diagnose, treat, or prevent serious or life-threatening conditions caused by chemical, biological, radiological, or nuclear threat agents, when there are no adequate alternatives.
As there are no commercially available diagnostic tests approved by the FDA for the detection of Zika virus infection, the agency decided an EUA was crucial to ensure timely access to a diagnostic tool.
The FDA issued the EUA for the Zika MAC-ELISA test based on data submitted by the CDC and on the US Secretary of Health and Human Services’ declaration that circumstances exist to justify the emergency use of in vitro diagnostic tests for the detection of Zika virus and Zika virus infection. This EUA will end when the Secretary’s declaration ends, unless the FDA revokes it sooner.
