The US CDC has suspended diagnostic testing for approximately 30 infectious diseases, including rabies and mpox, based on a list of temporarily unavailable tests on the CDC website. The reasons for the pause in testing remain unclear, although such pauses are not unusual, according to experts. Still paused CDC testing may increase delays as alternatives are sought, and local public health laboratories often have limited resources for infectious disease testing.

The CDC routinely reviews the tests maintained by its laboratories as part of its commitment to laboratory quality and efficiency, and regularly pauses some tests while reviews and changes are made as part of this process, Kelly Wroblewski, senior director of infectious diseases, Association of Public Health Laboratories (APHL), told Medscape Medical News. “CDC is currently undergoing a round of internal reviews following ongoing quality improvements, so we are seeing a higher than usual number of pauses,” Wroblewski noted.

For several common infections, notably the varicella zoster virus and Epstein-Barr virus, the CDC is not the only resource for testing, and commercial labs can conduct these tests.

The pauses in testing are inconvenient, Wroblewski said. However, public health has always found alternative sources of testing, most often at another public health laboratory but sometimes through commercial or hospital laboratory partners, she said. “The inconvenience comes from reviewing and complying with a new laboratory’s submission practice, enrolling in their ordering and reporting systems, and possibly paying a fee for a test that CDC offers at no cost,” she noted.

In many cases, such as parasitology, the clinical implications of limited test availability from the CDC are minimal because testing is available at commercial laboratories, although there are cost implications for a health department, Wroblewski said. For other diseases, such as human rabies, the CDC and a small number of public health laboratories are the only labs providing testing, so the potential impact is greater, she said. “Luckily, rabies tests are rarely ordered or needed for clinical care, which is why so few laboratories perform them,” she added. The public health laboratories that perform those tests are able to absorb anticipated volume until CDC testing is restored, she added.

Clinical Considerations

In practice, lack of clarity on where to receive testing in the absence of availability at CDC could lead to delays in ordering a test as clinicians and public health professionals seek alternative testing, Wroblewski told Medscape Medical News.

“Testing resources are critical for identifying infectious diseases with public health impact,” Robert H. Hopkins, Jr, MD, medical director of the National Foundation for Infectious Diseases, told Medscape Medical News.

“While some tests are available in state and commercial labs, the methods and standardization may differ from those used at CDC,” said Hopkins. Access to alternative testing also may be more limited in resource-constrained areas, he added.

However, the risk is greater that testing may be unavailable for less common, but serious diseases, such as rabies and poxviruses, or for emerging threats not commonly seen in the US, Hopkins said.

In cases of outbreak-associated testing, public health departments that rely on the CDC are not equipped to absorb costs of using commercial labs to fill the gaps, and often don’t have the mechanisms to recover those costs through health insurance, Wroblewski noted. Having centrally available testing at the nation’s public health agency is necessary to ensure efficient and effective responses to public health threats, she added.

Hopkins and Wroblewski disclosed having no financial conflicts of interest.