Hologic, a maker of diagnostic tests, said Wednesday that it is launching a new test for Covid-19 and that it could produce 1 million of them a week, a pace that would significantly expand testing capacity in the United States.
Over the last seven days, the U.S. conducted 1.3 million tests, a rate that has remained about the same over time. Experts, including a group assembled by the Rockefeller Foundation and a team at Harvard, in an analysis for STAT, have said that millions of tests a week will be needed in order to sufficiently test for infections with SARS-CoV-2, the virus that causes Covid-19.
Hologic already has a test for the virus that runs on its Panther Fusion system, and is based on the same technology as most Covid-19 tests, the polymerase chain reaction, or PCR. But because the Panther Fusion system is used by fewer laboratories, and because test kits for it are more difficult to manufacture, supply has been limited. Hologic has so far provided 800,000 of these kits, the company said.
The new test, which runs on a different version of the Panther system, uses a proprietary technology to test for the virus. It has not yet been granted an emergency use authorization by the Food and Drug Administration, but Hologic will make the test available to laboratories that are regulated by a different set of regulations, the Clinical Laboratory Improvement Amendments, which allow tests to be used under the regulation of the Centers for Medicare and Medicaid Services. The company will be applying with the FDA for an EUA.
Immediately, a “bolus” of 3 million tests will be available to CLIA labs, said Maurice Exner, a vice president of R&D at Hologic. Starting in mid-May, the company is aiming to produce a million tests a week. Exner said there are 1,000 Panther machines currently in use, and the company will work to manufacture more.
Exner said that although the type of clinical studies that are conducted in normal times have not been done, tests on samples show that the test’s ability to detect the virus should approach 100%. In similar tests for influenza, he said, sensitivity (the ability to detect the virus) was more than 99%, and specificity was 97.9%. The latter number was made lower, he said, by the fact that the Panther detected viruses that a comparator machine could not detect.
Simply manufacturing more test kits does not guarantee that patients will be able to get a test done, however. The testing rollout in the U.S. has been marked by snafus including shortages of viral media, used for transporting samples, to nasal swabs.
“Given that we are effectively at a million or so tests per week right now, adding another million to our capacity is not insignificant,” said Michael Pellini, a venture capitalist at Section 32 and one of the authors of the Rockefeller Institute’s report on testing. “Remember that we need to go to tens of millions per week, or even per day, but every step does count.”
However, Pellini said, more changes will be needed. “In parallel with a focus on pure test capacity, we have to do a much better job of marrying that capacity to testing demand,” he said. “If we don’t continue to fix the inefficiencies within the system, the supply and demand mismatch will just continue and platforms will not be fully utilized.”
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Given the push to test more asymptomatic persons (at nursing homes and among workers in health care and others providing essential services) a specificity of 97.9% is probably too low. Using a test with such low specificity to assess populations which may have a low prevalence of disease will result in a large number of false positives and a low predictive value positive. Perhaps such a test might be followed by a confirmatory test with higher specificity. But without stronger evidence, we might not be prepared to quarantine for a couple of weeks persons with a positive test.