Better Diagnostic Tests Are Key to Zika, GAO Report, Experts Say

March 4, 2016

The Government Accountability Office is raising concerns over the lack of validated diagnostic tests for the Zika virus — something that may mask the true extent of the outbreak.

At a hearing of the House’s Oversight and Investigations Subcommittee, Timothy Persons, chief scientist at the GAO, said there are two Zika diagnostic tests in use but not yet commercially available in the U.S. Both, however, have limitations.

The reverse transcription polymerase chain reaction and Immunoglobulin M followed by the Plaque Reduction Neutralization Test can detect infection only during the period of illness when the virus is present. While the PRNT test is the most specific for antibody detection, it is cumbersome and not suitable for screening a large number of individuals, according to Persons.

Late last month, the FDA issued an emergency use authorization for the CDC’s Zika Immunoglobulin M Antibody Capture Enzyme-Linked Immunosorbent Assay. However, Zika MAC-ELISA may confuse practitioners because it is unable to differentiate between infection with Zika and dengue.

“Adding to the limitations of these diagnostic systems are limited numbers of facilities able to perform definitive confirmatory testing, particularly in the developing world,” Persons says.

Anthony Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases, testified that his organization is developing a mouse model of Zika virus infection to test new diagnostic and therapeutic tools.

President Barack Obama also has made fighting Zika a priority. In a supplemental budget request, he asked for $10 million for the FDA to research and develop medical products and blood screening assays for the virus.

Threats and Response

In response to new infectious diseases, including the Zika outbreak, AdvaMedDx, which represents the diagnostics industry, held a briefing on March 3 in Washington, D.C. The event drew government officials and other interested parties to discuss strategies to address the threats.

Beth Bell, director of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases, said tests are a critical component to success in protecting people from infectious diseases. She pointed to two recent infections that resulted in unexpected results — Ebola and Zika.

“Diagnostics are pivotal to stopping outbreaks, and they inform much of our infection control and prevention efforts. Microbes are changing all the time, so we need new tools and methods to stay one step ahead of these microbes, as they continue to evolve and surprise us,” she said.

Tests are needed to be able to quickly diagnose patients. However, “we don’t just need new tests, we need accurate tests,” stressed Steven Binder, senior director of technology development at Bio-Rad Laboratories.

“We don’t want tests that are going to have a lot of false positives, which will then lead people to the conclusion that they have a disease which they may not have,” he said.

Read Persons’ testimony here: www.fdanews.com/03-16-GAOZika.pdf and Fauci’s testimonty here: www.fdanews.com/03-04-16-Fauci.pdf. — Jonathon Shacat