“I don’t know how effective the grouping will be, the impetus for the grouping really comes from the White House and [coronavirus coordinator Deborah] Birx and the group that it leads primarily because it’s an easy way to build numbers, ”he said. “I think they just want to get the numbers up,” he added later.
Blank said the cluster will not hold test supplies, including hard-to-find chemical reagents, if the overall prevalence rate is higher than 4-5 percent in a given community.
Still, some commercial labs are exploring whether they can pool the site, said Julie Khani, president of the American Association of Clinical Laboratories. “Pooling can provide a means to minimize reagent use and maximize test availability,” he said. “However, sample pooling has limitations, particularly in high-prevalence settings.”
Clustering can also reduce the sensitivity of tests. If a person in a sample group is in the early stages of a coronavirus infection and is just beginning to clear the virus, it may not be detected if other members of the group are not infected. Their negative samples could dilute the weak positive sample, Blank said.
FDA chief diagnostic officer Tim Stenzel echoed that concern in a July 1 call to the industry. The agency is asking laboratories and test manufacturers to seek emergency clearance for test pooling procedures. But the first data the FDA has reviewed suggests that the approach may produce a higher percentage of false negatives than individual tests.
“Unfortunately it won’t be a panacea,” said Stenzel. “Yes, it will address the reagent shortage. Yes, it can expand our ability to screen more and more patients with the given infrastructure we have, but almost all clustering schemes will reduce the sensitivity of the assay.”
Still, several public health experts said that, in the right environment, clustering can help expand desperately needed tests in areas where the virus is spreading at a low to moderate level.
A HHS spokesman said the health department expects the US to be able to perform 60 million individual coronavirus diagnostic tests in September, with another 40 million samples analyzed in groups.
Representative Max Rose (DN.Y.) says the Trump administration should aim to examine an even greater number of samples through pooled tests. It is lobbying Giroir and the White House to quickly implement the cluster across the country using funds from the Paycheck Protection Program and the Health Care Improvement Act.
“They’ve been playing hot potato. They say it is a technology problem, a financing problem, an orientation problem, a bureaucratic problem, “Rose told POLITICO. “Approval is only the first step because then it becomes an operational problem. I want to see group tests in New York City, there is no better place to do group tests. “
The Rockefeller Institute’s latest testing plan, which argues that at least 30 million tests are needed per week, also identifies clustering as a potential way to identify people infected but showing no symptoms.
Mark McClellan, who served as FDA commissioner and CMS administrator under George W. Bush, said the grouping could be a good way to evaluate preoperative patients in hospitals and people who return to work.
“Pooled tests work best when the positivity rate is expected to be very low,” McClellan said. “It is not something you want to do for symptomatic people or when you are evaluating people who have close contact with people exposed to the virus. But it is potentially very useful in settings like nursing homes where there is no active outbreak.”
Once the rate of new infections declines and test response times accelerate, clustering can be considered more seriously as a method of evaluating large numbers of people, according to Heather Pierce, regulatory adviser for the Association of Medical Colleges. American people.
“Our testing strategy as a nation is woefully behind where we need to be,” Pierce said. “Group testing is a very attractive and potentially very useful tool. The key is when and how it is used. “
