CDC denies California and Washington request to validate high-volume measles test

The US Centers for Disease Control and Prevention (CDC) denied a request from California and Washington to validate a new high-volume measles test, according to a letter from the West Coast Health Alliance to CDC director Erica Schwartz. The states asked in May and waited two months before the agency cited “other competing priorities,” the letter says.

The alliance’s letter was signed by health officials in California, Hawaii, Oregon and Washington. It asks Schwartz to reconsider and validate a rapid, high-throughput measles test ahead of major outbreaks, and to create protocols for testing other high-priority pathogens for future emergencies.

An HHS spokesperson, Emily Hilliard, said the CDC is “ensuring state and local health departments have the support needed to strengthen measles detection and outbreak response” and is “prioritizing emerging technologies” for the measles outbreak. Hilliard did not answer questions about whether the CDC plans to validate a high-throughput measles test or assay.

Public health officials say such a test would “dramatically strengthen” laboratories’ ability to respond quickly to outbreaks, improving preparedness for known pathogens such as Ebola or hantavirus as well as emerging threats. Currently, labs rely on lower-volume tests for measles, such as individual polymerase chain reaction (PCR) tests.

Existing equipment, missing validation

During the Covid pandemic, most public health labs bought high-volume equipment, including the Hologic Panther Fusion, a PCR platform that can process up to 500 tests in eight hours. But there is no high-throughput test to diagnose measles that has been validated by the CDC, the letter says.

Texas state laboratories developed such a test during the measles outbreak in west Texas last year, but they have not distributed or published the protocol. ARUP Laboratories, a national academic non-profit reference laboratory, published its measles assay in the Journal of Clinical Microbiology in December. The CDC could validate that or another protocol so other public health labs can run diagnostic tests, the alliance says.

Speed matters in an outbreak

High-throughput tests process many samples at once, and automated instruments can be faster and easier than manual testing. Benjamin Bradley, an assistant professor of pathology at the University of Utah and medical director of virology at ARUP, said one major advantage is “more flexibility.” In a measles outbreak, he said, time is “really of the essence.” One measles patient can infect 12 to 18 other unvaccinated people, and the virus can linger in the air for two hours.

Quicker testing can help curb an outbreak by identifying and isolating positive patients sooner and speeding contact tracing. It also means officials can promptly offer vaccines to anyone exposed who is not already vaccinated; vaccines taken within 72 hours of exposure can prevent infection.

There are no commercially available tests for measles; current tests are developed by laboratories. Validating and publishing the process for creating these tests is crucial for labs to be able to create and conduct them. Bradley said labs essentially have to do the science themselves, which is burdensome, and that sharing protocols helps.

The CDC has reportedly completed studies on the Texas and ARUP assays “but they were not full validations or a comprehensive comparison,” the west coast officials wrote. The alliance asked Schwartz to develop a measles diagnostic assay for the Panther Fusion and publish the protocol so any lab can run the tests. The letter argued that without high-throughput capacity, a large outbreak in their region would be harder to scale up diagnostic testing appropriately, impairing patient care and public health investigation.

Source: The Guardian World.