Do You Have A Testing Plan In Place?
Updated: Aug 12, 2021
“Testing” in the Covid-19 era has caused more confusion and consternation than almost any other topic associated with this disease (besides treatment-related issues of course). Due to this uncertainty, many businesses are unsure what testing for Covid-19 their employees need to ensure a safe return to work.
Mainly, businesses want to know how to screen their employees to minimize infections to other co-workers or clients. Unfortunately, there is currently no consensus standard. Contributing to the noise include no shortage of opinions, a multiplicity of the tests, evolving controversies surrounding the accuracy of the tests, and the underlying utility of the tests.
There are three basic types of tests for Covid-19: PCR-based tests, the antigen-based tests and the antibody-based tests. Currently, workplaces have essentially a choice of testing for Covid-19 with a PCR test or an antibody test since the antigen test is not widely available.
PCR-based tests look for active Covid-19 disease. PCR tests look for a genetic portion of the virus causing the disease referred to as Covid-19. Someone with a positive PCR test should be considered to be contagious for Covid-19 and treated accordingly (i.e. quarantined and referred to a medical facility or professional). These tests are used to diagnose someone with current symptoms of Covid-19 or to screen for someone who is at risk for having the disease such as a family member having active Covid-19 disease. They are not considered tremendously valuable for Covid-19 screening as the PCR tests only represent the individual’s Covid-19 status at that point in time. Individuals could easily contract the disease subsequently after the test. Occasionally, these tests are used justifiably for screening large groups such as sport teams who will interact closely together after travel from different locations.
Most importantly, these PCR tests are extremely uncomfortable for the individual. They are most commonly performed through and oral or nasal swabs that are 6 inches long. Lately, some tests are also capable of detecting Covid-19 through PCR in saliva. The nasal swab test require moderate training for the person performing the test. Due to this discomfort, the skill needed for the test, and the individual virus characteristics for each patient, these nasal swab PCR tests were initially accurate only 70% of the time in diagnosing active Covid-19 infection. The saliva-based tests were considered less accurate when first put on the market but those features may be changing.
Antibody tests for Covid-19 are surrounded by a great deal of controversy and misinformation. They look for the presence of antibodies to Covid-19 and can be performed with a fingerstick or actual blood draw. Someone whose blood has antibodies to Covid-19 was most likely infected with the Covid-19 virus, even if they were not symptomatic. Three types of antibody classes exist, IgA, IgM, and IgG. Most Covid-19 antibody tests look for IgG or IgM. In general (though individual tests and sources differ), IgA peaks early in the disease around day 2-5, while IgM peaks later days 5-14 and IgG is highest after 2 weeks.
Currently, antibody tests are used for two reasons: to screen someone for active Covid-19 disease and to assess whether someone had past Covid-19 infection. Since the antibody levels peak 2-5 days (at least) after someone has had the beginning of the infection, this test will miss some people with asymptomatic early disease. If the test does show antibodies, it should be followed by a PCR test to understand whether someone has active or past infection. If it does not practically matter whether someone has active infection (such as the person is already quarantined or poses no future risk to others), the PCR test may be skipped.
To screen large groups, many businesses prefer the antibody test because it is much less uncomfortable to the individual and can be done much quicker. Additionally, some of the commercially available antibody tests can give results within 15 minutes whereas PCR tests still have to go to a local laboratory and can take 24-48 hours to turnaround and give a result. However, the antibody test is not nearly as effective a screening tool as it does not reveal whether the individual has active current disease and is contagious. Additionally, both tests can yield some false-negatives in the early stages of the disease.
Antibody presence for Covid-19 may indicate that the person may be less likely to contract Covid-19 disease in the future. In other viral infections, antibody presence is thought to confer immunity to that disease. While this situation may prove similar in Covid-19 disease, nothing has been proven in medical studies to substantiate this. Indirect evidence does exist in that there are not many case reports of people being infected twice by Covid-19 so previous infectious is probably protective. Early reports that a positive antibody test could be an "immunity pass" have been rightfully questioned.
Several other issues also cloud the situation for antibody testing. Individuals who had a common cold from a different strain of coronavirus than that of the Covid-19 strain may also test positive for the antibody but not have had the Covid-19 disease or subsequent protection. Also, some scientists feel the presence of “neutralizing antibodies” are important to protection from future viral disease but the commercially available Covid-19 tests do not specify their test for this variant. Additionally, new studies show that antibodies levels may decrease after 3 months or so for Covid-19. In other viral diseases (such as hepatitis B), a minimum level of antibodies is necessary to offer disease protection but that is not universal for other viral disorders. No one knows currently whether the antibody level is important for Covid-19 disease protection. Also, the disease may be changing strains (like influenza) so protection may only exist for 10-12 months. If this is the case, a Covid-19 vaccine may need to be modified every year (like the influenza vaccine).
Quite simply, scientists and clinicians cannot state for certain that Covid-19 antibodies give protection (though they probably do).