CDC’s Test for Bird Flu Works, but Has Issues.

Originally published by Medpage Today. 

The CDC says a glitch in its bird flu test hasn't harmed the agency's outbreak response, but it has ignited scrutiny of its go-it-alone approach in testing for emerging pathogens.

The agency has quietly worked since April to resolve a nagging issue with the test it developed, even as the virus swept through dairy farms and chicken houses across the country and infected at least 13 farmworkers this year.

At a congressional hearing on July 23, Rep. Brett Guthrie (R-Ky.) asked about the issue. "Boy, that rings of 2020," he said, referring to when the nation was caught off guard by the COVID-19 pandemic, in part because of dysfunctional tests made by the CDC. Demetre Daskalakis, MD, MPH, director of the CDC's National Center for Immunization and Respiratory Diseases, responded that the agency rapidly developed a workaround that makes its bird flu test reliable.

"The tests are 100% usable," he later told KFF Health News, adding that the FDA studied the tests and came to the same conclusion. The imperfect tests, which have a faulty element that sometimes requires testing a sample again, will be replaced soon. He added, "We have made sure that we're offering a high-quality product."

Still, some researchers were unnerved by the news coming 4 months after the government declared a worrisome bird flu outbreak among cattle. The CDC's test is the only one available for clinical use. Some researchers say its flaws, though manageable, underscore the risk of relying on a single entity for testing.

The problem came to light in April as the agency prepared to distribute its test to about 100 public health labs around the country. CDC officials detected the issue through a quality control system put in place after the COVID test catastrophe of 2020.

Daskalakis said the CDC's original test design was fine, but a flaw emerged when a company contracted by the agency manufactured the tests in bulk. In these tests, one of two components that recognize proteins called H5 in the H5N1 bird flu virus was unreliable, eliminating an important safeguard. By targeting the same protein twice, tests have a built-in backup in case one part fails.

The agency developed a fix to ensure a reliable result: If only one of the two parts detected H5, the test was considered inconclusive and would be run again. With the FDA's blessing, the CDC distributed the tests -- with workaround instructions -- to public health labs.

Kelly Wroblewski, MPH, director of infectious diseases at the Association of Public Health Laboratories, said the results of the tests have not been ambiguous, and there is no need to discard the tests.

Still, the agency has asked a different manufacturer to remake the faulty component so that 1.2 million improved tests will be available soon, Daskalakis said. Some of the updated tests are already in stock at the CDC, but the FDA hasn't yet signed off on their use. Daskalakis declined to name the manufacturers.

Meanwhile, the outbreak has grown. Farmworkers continue to lack information about the virus and gear to protect themopens in a new tab or window from it. Rural clinics may miss cases if they don't catch a person's connection to a farm and notify health officials rather than their usual diagnostic testing laboratories.