ROCHESTER, N.Y. (WROC) — With a rapid, 15-minute COVID-19 test, there’s a drawback. The accuracy isn’t what it would be for a test that takes longer and extracts DNA – also known as a PCR test.
This is all according to researchers at URMC, as they told us about the rapid testing used in schools starting this week. URMC also told us the test, Abbott BinaxNOW claims to have a 97% positivity rate for those with symptoms.
Some of our viewers have expressed to us, what’s the point of mass testing students without symptoms, if the accuracy isn’t what it could be?
Dr. Richard Zane, Chair of Emergency Medicine at UCHealth and University of Colorado Hospital, says when understanding the effectiveness of the antigen test, you have to consider the circumstance in which it’s used.
If we are looking at one person getting tested for their own insight, it’s not going to be your best bet, he says. The reason for this has to do with the test’s sensitivity to false negatives.
“The antigen tests have very high false negative rates,” said Zane. This sensitivity rate for false negatives makes the test unreliable for personal cases, he says.
But if we are using the test on a more widespread level, testing hundreds of people at once, Zane says the antigen test is a good tool for getting a sense of community infection. The reason for that has to do with the specificity of the test, in other words the percentage of true positives, which Zane says is high for the test.
“If you screen a large group of people, and they all test negative, that’s pretty reassuring … when a test is positive it is likely to be very positive. From a specificity perspective, it’s a pretty good test,” he said.
Imagine 1,000 people are tested, and no one tests positive. Zane says that result is much better than if 10 tested positive. While ten testing positive could actually be 20 or 50, considering false negatives, it’s still a good result for looking at a high number of people in a community.
“On a small group, individual basis, it’s not a good test,” said Zane.
Zane says keep in mind rapid testing is just one tool. If you test negative and are symptomatic, follow up with a PCR test – the more accurate test that extracts viral DNA – to be certain. If you don’t have access to a PCR test, go ahead and quarantine to avoid exposing yourself to others.
“A negative should not change your behavior in any way, it does not mean you don’t have COVID, it does not mean you can’t spread COVID it does not mean you are safe,” said Zane.
News 8 also reached out to URMC for a comment, as they were one of the sites where clinical trials for this test took place. URMC researcher Kian Merchant-Borna says with any public health tool, there is a balance. “It will give you some assurance but not complete assurance, it’s still important to be vigilant,” he says.
Merchant-Borna says he sees a day in the future, where the general public will be able to buy these tests in bulk at a drugstore, and test themselves before they go out and about.
In a statement Jonah Bruno from the New York State Department of Health says when it comes to rapid testing, the benefits are rapid turnaround at a low cost. The statement goes on to say:
“These benefits come with lower accuracy compared to molecular tests with higher accuracy but longer turnaround time. Testing groups of students in micro-cluster zones helps determine the prevalence of infection in the community. If positives are found in schools, contact tracing will help identify cases in the community, and additional actions can be taken to prevent further spread. If the number of positives found in schools is disproportionately high to the rest of the zone or community, the testing would be re-evaluated. To date, this has not been reported to DOH.”