COVID Testing
We have all heard that the key to preventing the virus from spreading is testing. But what types of tests are available and which one is the best?
As far as COVID testing there is not one test that is the BEST. It all depends on the person’s situation. The best way to determine which test is best for you is to work with your provider or pharmacist. Here is some information about the three different categories of tests that are available: PCR (a nasal or throat swab), Antigen (a nasal or throat swab) and an Antibody (a blood test).
PCR and Antigen are considered diagnostic tests as they can detect the virus earlier, while an antibody test detects antibodies later on. None are available to purchased directly by the consumer at this time.
PCR test is best to be used before or during symptoms. The virus is easily detectable within 7 to 10 days of illness. The test uses a process to test molecular breakdown of the virus. The Abbott ID Now test which delivers results within as little as 5 minutes is a PCR test.
An Antigen test is not reliable until symptoms exist. The peak or optimum testing time is about 3 to 5 days. The test is testing the coating of the virus.
The Antibody testing does not focus on checking the virus itself, but whether your immune system has built antibodies in response to the infection. It involves a small finger prick blood sample that takes at least 10 days to detect IgM antibody. Around 2 to 3 weeks later it can also detect IgG. These tests should be performed only on people that never had symptoms or it has been at least 7 days since their last symptom. If tested earlier, clinical reliability may be compromised.
More about Antibody testing…
There have been reports about fraudulent tests that are being sold. Here are a few things to watch for. As of now, there are no antibody tests on the market that have FDA approval, this will change with time. Testing kits are registering with the FDA and some have been granted an EUA (emergency authorization) by the FDA, but they are still not FDA approved. If you choose to receive an antibody test you will want to ask the person offering testing if they have checked and validated that the test has been registered with the FDA. In addition, tests that are on the market should have used PCR and not ELISA to validate their negative and positive results, as PCR is considered “Gold Standard” for COVID.
As far as the antibody test it tests for the antibodies IgM and IgG. IgM is the first antibody response to be detected. If IgG is detected and the level has become higher than IgM this means the maximum immunity response has occurred.
Keep in mind that these are qualitative tests not quantitative tests. This means it does not tell you how many antibodies, so it does not tell you if you are immune or how long you are immune. To measure immunity, you need to measure a titer, similar to a titer test performed after receiving your hepatitis B vaccines.
Therefore, Antibody testing does not tell you if you are immune but it does help in making decisions as far as when a person can stop being in quarantine and return to the workforce. It also helps with identifying donors for COVID-19 convalescent plasma.
In addition, look for the following to be labeled on a test:
1. This test has not been reviewed by the FDA
2. Negative results do not rule out SARS-CoV2 infection, particularly in those who have been in contact with the virus. Follow up testing with a molecular diagnostic should be considered to rule out infection in these individuals
3. Results from antibody testing should not be used as the sole basis to diagnose or exclude SARS-CoV2 infection or to inform infection status
4. Positive results may be due to past or present infection with non-SARS-CoV2 strains, such as coronavirus HKU1, NL63, OC43, 229E
