The FDA is making a panel of human plasma samples available to help developers of serological Zika virus diagnostics verify that their assays can distinguish Zika virus infection from infection with West Nile or dengue viruses. The panel comprises plasma samples from anonymous individuals infected with Zika, West Nile, and dengue viruses and is available to diagnostic developers who have interacted with the FDA through the pre-Emergency Use Authorization (pre-EUA) process and have serological tests that are at the final validation stage. Other developers interested in requesting a panel may also contact the agency.
“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 its EUA authorities,” commented FDA Commissioner Scott Gottlieb, M.D. “By providing manufacturers of these tests with standardized patient samples to use in properly validating these diagnostics, we will be able to better assess how well their tests perform. This is part of our effort to ultimately bring these tests through the FDA's formal review process to better ensure their reliability, and to enable broader access to Zika diagnostic testing.”
Blood diagnostic tests for Zika virus are broadly grouped into nucleic acid tests that identify viral RNA and serological tests that identify Zika virus antibodies. The FDA notes that serological tests have particular importance because viral RNA may only be detectable during a short window, but the development of antibody-based assays is challenging because it can be hard to distinguish between Zika virus antibodies and antibodies generated in response to the related dengue and West Nile flaviviruses. The FDA maintains that using the same serological panel to evaluate different devices available under EAU will help reliably compare the performances of different Zika virus tests.
The three serological tests for detecting recent Zika virus infection that have already been granted EUAs include Zika MAC-ELISA developed by the Centers for Disease Control (CDC), InBios International’s ZIKV Detect™ IgM Capture ELISA, and DiaSorin’s LIAISON® XL Zika Capture IgM.
Just last month, Swiss firm Humabs BioMed and the University of California, Berkeley published data demonstrating use of the company’s NS1 blockade-of-binding (BOB) ELISA antibody test to detect and differentiate recent and past Zika virus infections from other flaviviruses, including dengue.