The U.S. Food and Drug Administration on Wednesday issued an Emergency Use Authorization (EUA) to North Carolina pharmaceutical company Cellex for a new finger prick blood test that can detect an immune response SARS-CoV-2. This is not the first test to get the green light from the FDA: at least two dozen other tests that look for the virus’s genetic material on a throat swab have already received an EUA. But the Cellex test was the first for a blood test (another company claimed the honor earlier in the week, but then withdrew its request).
There is, however, a curious caveat in the test labeling and marketing materials. The authorization, like the ones before it, clearly states, “This test has not been approved or approved by the FDA.” So what does it mean to be authorized, but not approved?
In the context of the coronavirus pandemic, the FDA has endeavored to update its regulations for companies wishing to develop, manufacture and distribute tests, in order to balance the need for speed with the concern for safety that is, not to publish a test that tells people that they are not infected when they really are. The final word came on March 16, which describes the steps that companies must take to publish the tests. They are quite loose, especially when compared to earlier versions of the regulations, which, according to some, delayed the deployment of tests.
In short, genetic swab tests, which are used to diagnose a current infection, can be marketed and used as soon as they work in an initial trial with relatively few samples – even before the delivery of an AUS . The company must submit these test results within 15 days of their completion, and if the FDA issues the EUA, nothing changes much: it just means that the tests can continue to be sent to laboratories and hospitals (no test at home is not yet authorized). If the EUA is declined, the company should stop distributing the test and issue a reminder. Companies are allowed to request special exemptions at these stages of their state governments.
Authorization for these diagnostic tests for SARS-CoV-2 differs from full-fledged “approval” in two main ways.
First, the validation bar is much lower. FDA approval is a long and cumbersome process that usually involves multiple human trials involving hundreds of participants – first to make sure the product does no harm, and then to make sure it actually works. For an EUA, a company must essentially prove that the product works fairly well in a test with only a few dozen samples, obtaining the correct response at least 95% of the time for samples with a low viral load, and 100% of the time for higher viral loads and in virus-free samples. The process can be completed in weeks rather than months or years.
The second distinction concerns duration. An EUA only applies as long as the Secretary of Health and Social Services has made a public health emergency declaration, and only in the context of this particular emergency. Accreditation, on the other hand, is permanent (except the emergence of new data calling into question its safety or effectiveness).
“It is not a perpetual approval to use it forever,” said Matthew Weinberg, CEO of the Weinberg group pharmaceutical consulting firm, a company of the ProPharma group. “The FDA allows certain products that appear to be of value in the Covid-19 crisis, without the full set of test data, to provide relief where they appear to provide relief.”
For blood tests like that of Cellex, the bar is even lower: the FDA allows them to be distributed without even having to request an EUA. At least two dozen companies have told the FDA that they will do just that.
This is a bit counterintuitive, since blood tests are known to be less accurate in diagnosing infections than swab tests. (They detect the body’s immune response to the virus, which can appear a number of days after SARS-CoV-2 has taken hold in the body.) But the FDA requires that blood tests include another warning, advising users that the tests should not “Be used as the sole basis for diagnosing or ruling out SARS-CoV-2 infection.” This warning is still required for blood tests that receive an EUA.
The only reason to look for one, like Cellex, is for the marketing benefit of calling your test “FDA approved.”