One of the most frequently asked questions in the last few weeks is about Covid-19 tests. I’d like to take a few minutes to explain the facts and myths about these tests.
Quick Summary
There are two main categories of Covid-19 tests: antigen tests and antibody tests. These tests are only useful for epidemiology purposes to determine trends and geographical distribution and public health responses. They have minimal clinical values in determining the treatment of any individual person/patient.
Applicability of Tests
Antigen tests look for the presence of infectious agents while antibody tests look for the host immune response to the infectious agent. Clinically, antigen tests are used by the CDC and hospitals to confirm active infection on initial presentation. However, these tests have poor sensitivity in detecting Covid-19 especially during the initial stage of the infection when the viral load is low.
Antibody tests have no role in initially detecting a disease since antibodies are not developed by the host until the later stages of infection. Antibody tests are only useful in identifying previously infected persons (who have already developed antibodies against Covid-19). Again, it is useful only for epidemiology purposes for policy makers and the government to plan for resource allocation and response efforts.
For individual patients, doctors are treating everyone with viral-like illness as Covid-19 patients during this Covid-19 crisis, regardless of test results being positive or negative. A false negative can give false confidence to a Covid-19 patient and expose others to this infectious agent. False positives may cause unnecessary stress and a waste of medical resources. The easiest formula to take care of yourself is “If you have viral-like symptoms, just assume you have Covid-19. Stay home, stay warm, rest, and use supportive treatments, such as acetaminophen to relieve fever and aches." There is no need to do a test unless you are so sick that you require hospitalization.
Accuracy and Reliability of the Tests
The first category is the RNA nucleic acid and antigen test. This test is utilized to detect the presence of a new infection or active infection by identifying the presence of Covid-19. The overall sensitivity and specificity of tests varies greatly from 30% to 90% based on the quality of the test itself (makers, manufacturers), method of collection (nasopharyngeal, pharyngeal swab, sputum, or pulm samples), and timing of collection (early stage vs. late stage of an infection). Any test with sensitivity < 50% is really not much better off than a tossed coin.
The second category is the antibody test, which has various qualities depending on the manufacturers and processes. Again, this test has no utility in the management of a patient during the acute sickness stage. It may be useful only as an epidemiology tool.
I hope the above helps everyone to understand Covid-19 tests better. Please do not waste your time and money chasing down tests. You may even get exposed to Covid-19 running in and out of the medical facilities to get these tests.
From your CMO, please stay healthy and happy.