COVID-19 testing: Where we are and where we’re going

As COVID-19 vaccines become increasingly available throughout the country, we should remember that COVID testing still plays an important role in infection control.

“One thing we have seen is the emergence of better rapid testing in the form of antigen tests that are readily available to the marketplace,” said Dr. Joseph Petrosino, chair and professor of molecular virology and microbiology at Baylor College of Medicine. “We need to get tests down to single digit dollars in cost. If there is another pandemic or if we have another surge across the country, the only chance of keeping businesses and schools open is if we have rapid testing platforms that are robustly available and affordable.”

Rapid tests usually give results in 15 to 30 minutes, and the accuracy of these tests has improved. And, because rapid tests are constantly being evaluated against new variants, they should be able to detect the presence of the virus even if an individual has a new variant.

“If you are seven days past exposure to the virus, the best rapid tests can have about a 90% accuracy rate.”

There is the possibility of false negatives, but a positive test result from a rapid test is usually very accurate. Individuals who have symptoms of the virus but receive a negative rapid test result should seek a PCR test.

If the cost of the rapid tests decreases it would allow people to test themselves repeatedly, which would be beneficial for restaurants, concert venues, airlines and other industries that have been financially impacted by the pandemic. Individuals who are constantly exposed to the virus, such as healthcare workers, could test themselves every other day or every third day.

In the coming months, Petrosino said we may see a higher incidence of low-grade infections because the vaccine doesn’t guarantee complete protection against the virus but does prevent from severe infection, so vaccinated individuals can still get a milder form of the virus. Furthermore, as variants continue to emerge, some may be less susceptible to the immune response generated by current vaccines.

“We need to set up new paradigms for testing to make sure individuals don’t have breakthrough infection,” he said. “With milder COVID, you may be pushing the limits of detection with some of these rapid tests, but we just haven’t seen the data on how these tests perform. Robust levels of mild breakthrough infections can also lead to new, more threatening variants.”

According to Petrosino, there is a need for important technological advancements that enable PCR test samples to be rapidly screened for the presence of variants at the same time. Currently, labs wait to get a full batch of test samples before sequencing to see which variant is present in the positive samples.

“Thankfully, it’s not needed at this moment, but if you had a variant that the vaccine did not protect against, and we knew it needed to be treated differently, that’s when the testing and knowing the variant at the same time would be important,” he said. “There are investigative procedures that can be developed for that. We need platforms that can do it at the flip of a switch and we don’t have those quite yet.”

-By Dipali Pathak