Zika Antibody Detection Tests Go from Emergency to Commercial Clearance

 Over the past several years, the U.S. Food and Drug Administration (FDA) has issued Emergency Use Authorization (EUA) for over a dozen different tests for Zika. But on May 23, 2019, the FDA did something it had never done before: It authorized marketing of a diagnostic test for the Zika virus—specifically, Seattle-based InBios’ ZIKV Detect 2.0 IgM Capture Elisa for detecting immunoglobulin (IgM) antibodies in human blood, an assay previously cleared for emergency use only. Here’s the lowdown on the approval and its significance. Since then, two more Zika antibody detection tests with EUA status have gotten the green light to go commercial.

The Context: About Zika

 The Zika virus is spread to humans primarily through the bite of an infected Aedes mosquito. Although many people with Zika virus infection experience no symptoms, the virus can pose potentially serious risks to the public health. Links between Zika virus infection and neurological complications (i.e., Guillain-Barré Syndrome), as well as microcephaly (abnormal smallness of the head) and other poor outcomes associated with Zika virus infection during pregnancy, have increased the importance of having diagnostic tests available for Zika virus.

In 2016, the Centers for Disease Control and Prevention (CDC) announced that limited local mosquito-borne Zika virus transmission had been reported in the continental United States. In 2018 and 2019, no such local transmission was reported.

 The Commercial Breakthrough

 The ZIKV Detect 2.0 IgM Capture ELISA is designed to identify proteins (antibodies) produced by the body’s immune system when it tests for Zika virus infection in the blood. IgM antibodies indicate an early immune response. The test is for use only in patients with clinical signs and symptoms consistent with Zika virus infection, and/or who meet the CDC’s Zika virus epidemiological criteria, such as a history of residence in or travel to a geographic region with active Zika transmission at the time of travel. The FDA authorization doesn’t cover testing of blood or plasma donors.

Results of ZIKV Detect 2.0 IgM Capture ELISA are intended for use in conjunction with clinical observations, patient history, epidemiological information and other laboratory evidence to make patient management decisions. The assay also differentiates Zika IgM from those infected with other flaviviruses (such as dengue or West Nile virus) which cross-react with Zika antibodies.

Why Now + Why InBios?

 Moving beyond EUA to marketing authorization is a seminal shift in FDA policy. FDA Acting Commissioner Ned Sharpless, M.D., sheds light on the agency’s thinking. “At the onset of the Zika virus outbreak, when little was known about the disease or how to diagnose it, the FDA worked quickly with manufacturers to encourage the development of diagnostic tests and ensure they were available using our emergency use authorities,” Sharpless explained.

Comfort with the effectiveness of the InBios Zika assay enabled the agency to take the next step.  According to InBios, the assay was evaluated via testing 807 unique specimens—353 from test subjects at sites where Zika is endemic and 256 subjects at non-endemic sites. In samples from patients collected seven days or later after the onset of symptoms, the InBios Zika kit correctly identified over 90% of patients confirmed positive for Zika IgM and over 96% of patients confirmed negative.

Two More Tests Approved for Marketing

Since May, the FDA has extended the approval of two more Zika antibody tests from EUA to clearance for marketing:

• The Siemens Healthineers’ Advia Centaur Zika test (approved for marketing on Aug. 9, 2019); and
• The DiaSorin Liaison XL Zika Capture IgM Assay II for detecting Zika virus IgM antibodies (approved on Nov. 5).

The authorizations do not impact the availability of the other Zika nucleic acid diagnostics available under EUAs.

 Zika Tests with EUA Clearance from FDA