There are currently three ways to test for COVID-19, including an antigen test that was recently approved by the Food and Drug Administration.
We’ve all become more knowledgeable about viruses and testing than we probably ever imagined. Still, the various emerging ways of how to test for the coronavirus/COVID-19 or prior infection, their reliability and their usefulness can be confusing.
Here are some quick explanations of how to test for the coronavirus
PCR test for SARS-CoV-2 virus (COVID-19)
This is the most common right now. A sample is collected with a swab from people who already have COVID-19 symptoms.
How it works: A sample of mucus is taken from the nose or throat with a long cotton swab. If you’ve ever had a flu test, it’s pretty much the same method. The mucus is analyzed with reverse transcriptase-polymerase chain reaction (RT-PCR) technology that can detect the virus if the patient is actively infected.
The sample may be sent outside the health system to another laboratory or may be tested in the laboratory of the health system itself. Earlier in the COVID-19 crisis, this part of the process took as long as a week to get results. That has improved significantly and, depending on the equipment used, a result may be available in few hours to a few days. Further, there are some rapid tests that can deliver results in 13 minutes or less. These require specialized equipment to determine the results.
Pros: Currently, probably the most reliable to test for the virus itself. If you test positive, you’ll be expected to take precautions, particularly if you are sick or caring for someone.
Cons: If you tested negative, you are probably not infected at the time the sample was taken. The swabs may miss catching a sample of the virus and give a false negative test. The lag in getting results for most tests means it cannot identify someone who has been infected between the time the sample was collected and when results are known.
Antibody testing (serology)
This test will show whether you’ve developed antibodies from a COVID-19 infection or possibly from a related coronavirus. Whether the antibodies will protect you from a second infection isn’t known yet.
How it works: Using a blood sample, the test looks for antibodies in your system. Your body will develop detectable antibodies as long as a week after infection, so the test isn’t useful for active diagnosis.
Pros: A positive test shows you had been exposed to the virus, whether you had symptoms or not. The information could make you eligible to donate blood plasma that could be provided to a gravely ill patient as an experimental convalescent plasma treatment.
Cons: At this time, it isn’t certain that a positive test means you’re immune. If you test positive and you have symptoms, you’ll still need a test for the virus itself.
The FDA issued its first approval for an antigen test on Friday, May 8. The test looks at samples collected via a swab from the nose and provide results in minutes. Similar technology is used for rapid strep testing.
How it works: Using samples from a nasal swab, the test can be conducted in the health care provider’s office and quickly can detect proteins associated with the virus.
Pros: Positive tests are very accurate, but aren’t as sensitive as PCR tests; less costly and possibly more easily scaled to millions of tests per day, especially once more manufacturers are approved, according to the FDA.
Cons: Higher chance of false negatives than PCR tests, so a negative antigen test does not rule out infection. Negative antigen tests may need to be confirmed with a PCR test to inform treatment decisions or prevent spread.