COVID Testing, April 24, 2020
Thoughts on COVID Testing, April 24, 2020
With the continued (but, hopefully, slowing) spread of COVID-19, there is a lot of discussion about the need for more testing. But what are we testing? How does it work? What does it mean?
Nasal Swab Testing – this has been the standard test available for the last several weeks. This test takes a sample of mucous from the nasopharynx (way back there), and the lab looks for viral RNA specific to COVID-19. This test is very accurate if positive, but could be misleading if negative. It’s possible to test negative early in the disease, if the sample is not collected properly, or if there’s just not enough viral cells in the sample to show positive. So, a negative test is not a guarantee that someone is COVID-free.
Finger-stick Testing – This was the most anticipated change in our battle to control Corona, as it would allow for rapid testing for current or previous infections. These tests check for antibodies, created by your immune system, to fight the infection. Certain antibodies appear fairly early in the infection (3-5 days), and some come later and last a lifetime (theoretically making you immune to COVID). The finger-stick versions of antibody testing would give point-of-care access to results in 10-15 minutes. They would be less expensive, and more widely available, than nasal swab testing. Unfortunately, there were concerns about the accuracy of these tests, and most of them did not receive FDA approval for use in clinics. Instead, they were only approved for use in complex labs. This negated the access, low cost and rapid results that were expected to be the main benefits of finger-stick testing.
Blood Draw Testing – The most recent addition to our testing options is drawing blood and sending it to a reference laboratory for antibody testing. This testing is similar to finger-stick testing, in that it is looking for antibodies indicating recent or previous infection, as well as potential immunity. The techniques used to test in the laboratories, although new for COVID, are well-tested processes that should yield consistent, reliable results. The initial cost should be reasonable, and the turnaround time should only be about 1-2 days. This test is probably most useful in determining someone’s previous exposure to COVID, but could be used, in conjunction with nasal swab testing, in patients with exposure to, or symptoms of, COVID-19.