Serological tests use a participant’s blood, serum, or plasma to identify the presence of antibodies. This allows a determination of active infection and whether someone has built up an immunity to the virus based on past exposure. Serological tests detect antibodies present in the blood when the body is responding to a specific infection, like COVID-19. They detect the body’s immune response to the infection caused by the virus rather than detecting the virus itself. In the early days of an infection, when the body’s immune response is still building, antibodies may not be present in detectable levels. This limits the test’s effectiveness for diagnosing COVID-19 and is why it should not be used as the sole basis for diagnosis. Currently, authorized serological tests for COVID-19 measure IgM and/or IgG antibodies. Since IgM antibodies may not develop early, or at all, in infected participants this type of antibody test is not used to rule out COVID-19. Since IgG antibodies generally do not develop until later, this type of antibody test, even though it is more specific to COVID-19, is not used to rule-out the infection in an individual. Typically, IgM peaks at day 5 and lgG peaks at 14-21 days. IgM appears first and then slowly drops off. As IgM disappears and IgG picks up, this indicates the participant is likely entering recovery and at some point no longer contagious. The test is easy to administer, offering reliable results in 10 minutes.

Polymerase Chain Reaction (PCR) Testing is a laboratory test to diagnose COVID-19 infections based on viral DNA. The test involves a nasopharyngeal swab that looks like a long Q-tip and draws mucus from the back of the participant’s nasal cavity where it meets the throat. The swab is then inserted into a vial and is shipped to a laboratory where lab techs or machines use reagents to extract the viral RNA. An enzyme, Reverse Transcriptase, is used to convert the RNA into DNA and the DNA is replicated many times to make it detectable. PCR tests are able to identify the virus before the antibody test. Serology tests are not very effective at identifying infection in the pre-symptomatic or early symptomatic stages. PCR begins to lose sensitivity by 3-6 days. However, IgM serology starts becoming very sensitive and showing positives at 5 days. This means, there are situations in which a participant comes in for testing around this time and a PCR based test could be negative, but IgM could be positive. There is a period of time where IgM becomes more sensitive than PCR. 

It has been determined that the best and most effective way to test for COVID-19 is to administer both the serological and PCR tests. BRHPC testing staff will first administer the serology test. The serology test involves getting a sample of the participant’s blood by pricking the finger. The blood is then placed onto a cassette and a buffer added. Results become available in 10 minutes. The participant’s results determine whether isolation and follow-up procedures are necessary. As discussed above, the serological test should be used in tandem with the PCR test, which BRHPC will also administer. The PCR test involves collecting a specimen through a nasopharyngeal swab and sending the specimen to the lab to be processed. The isolation and follow-up measures depend on the results of the two tests as follows:

• If the participant is symptomatic at the time of testing, they should be quarantined and a follow-up appointment scheduled with their primary care physician, as BRHPC only tests individuals wihtout symptoms.
• If the participant is asymptomatic and neither IgM or IgG is detected, then the participant is presumed negative and free of COVID-19. No isolation measures need be taken pending results of the PCR test.
• If the participant is asymptomatic, and the serological test indicates the presence of IgM alone, then the participant must take isolation measures pending results of the PCR test.
• If the participant is asymptomatic and the test indicates the presence of IgG alone, the participant is considered to be in the late stages of recovery and not contagious. No isolation measures need be taken pending results of the PCR test.
• If the participant is asymptomatic, but the serological test indicates the presence of both IgM and IgG, then the participant is considered to be in the early stages of recovery and must take isolation measures pending results of the PCR test.