COVID-19 test accuracy raises concerns among scientists
INDIANAPOLIS (WISH) — Some scientists have voiced concerns about the accuracy of COVID-19 tests.
In a perspective paper published in The New England Journal of Medicine, authors say while “there is broad concern that widespread SARS-CoV-2 (COVID-19) testing is essential to safely reopening the country … test accuracy may prove a larger long-term problem.”
Test-kit development happened rapidly under the Food and Drug Administration’s emergency-use authorization and was distributed quickly. The urgency to stop the virus from spreading through testing became the No. 1 priority.
But now, researchers are taking a step back to take a closer look at the implications of this decision, asking, “What if test outcomes aren’t as accurate as we first thought they were?”
A diagnostic test can be inaccurate in two ways. First, there’s what’s known as a “false positive,” when a person is tested — in this instance for COVID-19 — and the result shows they have the virus when they really do not. The second, more consequential outcome is a “false negative,” when a person is tested and the result is negative, but the person does have the virus.
False negatives are dangerous because a person may be unknowingly spreading the virus to others.
Authors of the article, “False Negative Tests for SARS-CoV2 Infection — Challenges and Implications,” say three things are necessary to determine testing accuracy: analytical sensitivity, analytical specificity and clinical sensitivity.
Analytical sensitivity refers to the smallest amount of a substance a test can detect. Since COVID-19 is complex and made up of many things, analytical sensitivity is determined when any part of the virus is discovered.
According to the National Center for Biotechnology Information, analytical specificity refers to the ability for a test to measure one specific substance and the likelihood the sample will be negative for all other germs, bacteria or viruses.
Clinical sensitivity refers to the proportion of patients who both test positive for the coronavirus and actually have the virus.
It’s unclear if any of the FDA-authorized coronavirus tests distributed across the country have been evaluated against these three criteria.
One study from Wuhan, China, shows test-kit inaccuracies. Researchers tested 213 patients hospitalized for COVID-19. They collected 205 throat swabs, 490 nasal swabs and 142 mucous samples. Of the samples collected, 11% of mucous collections, 27% of nasal and 40% of throat swabs gave a false negative.
“If SARS-CoV-2 diagnostic tests were perfect, a positive test would mean that someone carries the virus and a negative test [would mean] that they do not,” authors write in the report. “With imperfect tests, a negative result means only that a person is less likely to be infected.”
When it comes to a pandemic that has swept the globe, the difference between the two has enormous implications.