We are (at a minimum) 5 months into the worldwide Covid-19 pandemic that has upended all of our lives. We have been told "testing, testing, testing" is needed and will be our way out to get back to normal. There is still massive confusion about testing so let's try and make some sense out of it.
First some definitions:
The Covid-19 nasal or throat swab test- This is the test that we are promised "Anyone can get" and most of the time it will reliably diagnose Covid infection. These tests are now provided in labs, drug stores, drive through testing and some specialized medical offices. Because they deal with patients who might be infected, the front line testers have to have full PPE to protect against the virus. Depending upon the test, the results are ready between 24 hours and up to a week. This test has up to a 20% false negative rate, meaning it will say there is no infection, even if a person is infected. The test has to capture the virus when it is most active to be positive and the test has to be processed correctly to give accurate results. If a person has symptoms that are suspicious of Covid with a negative test, they should have a follow- up test before it is considered accurate.
This test tells you if you have Covid-19 at that point in time.
The Covid-19 antibody blood test- This test uses special chemiluminescent immunoassay technology or lateral flow assay technology to test blood samples and see if a person has antibodies showing current or past infection with Covid -19.
This test is currently very problematic and I do not recommend patients get this test as it does not function as an "Immunity Passport" and allow a person to feel safe with Covid. There are many hundreds of these tests that flooded the market when the FDA originally let them be sold without strict guidelines. Even the ones that are now approved do not give us the information we need.
We don't know what positive means because it can pick up other corona viruses
We don't know if having the antibody confers immunity and we don't know how long immunity would last.
We don't know if a person who had Covid-19 could get it again
Most insurance is not covering this test
The current antibody test is useful for public health experts to figure out the prevalence of the virus, the hot spots and the fatality rate. But even those studies need to be very carefully done to capture the entire population since we know Covid-19 is disproportionate in it's infection rate and severity.
Patients often ask for the antibody test because they want to travel, visit grandparents, return to school, return to work or just know if they are personally safe. I wish we could give them that answer but it's not yet ready for prime-time.