You’ve been feeling lousy -- and since you’ve heard that just about any symptom could be a sign of COVID-19, you do the smart thing and get tested. To your surprise, the test comes back negative.
Negative? But I feel horrible! Could the test have been wrong?
Yes, that’s possible.
COVID-19 tests, whether a rapid antigen test or a PCR test sent to a lab, do tend to be accurate on the positive side (if the test says you have COVID, you most likely do), but they can sometimes deliver false-negative results, especially the antigen (rapid) tests. Meaning, if the results are negative, there could still be a chance you have COVID-19. If you get a false-negative result, you could end up spreading it to other people while thinking that you’re in the clear.
A few reasons false-negative results might occur:
- A person gets tested before enough viral particles have accumulated in the nasal passages for the test to detect them. In general, most people who are infected with SARS-CoV-2 won’t test positive until several days (or even a week) after infection.
- The swab test was not administered correctly, and thus did not pick up enough secretions from the nasal passages to deliver an accurate result.
- The sample you gave with the swab or spit got contaminated.
- The swab wasn’t kept at the right temperature before getting analyzed.
- The chemicals used in the test didn’t work properly.
The timing aspect seems to be particularly important here. Looking at the most commonly used type of COVID-19 test (the PCR test, typically done with a swab), researchers found that the test can return a false-negative result as often as 67% of the time during the first 4 days of an infection.
So what does all of this mean? First, if you got a negative result from a rapid antigen test, consider getting a PCR test because it’s more accurate at detecting the virus. Second, if you feel sick you should act as if you have COVID-19, no matter what the test results say. That means isolating yourself at home for 10 days (if you live with other people, wear a mask in your home and stay as far away from others as possible, in a separate room if possible) and calling your doctor to report your symptoms and get personalized guidance about what to do next.
If you got a test because you were exposed to someone with COVID-19, but you don’t have symptoms, you shouldn’t assume a negative test result means you can go back to normal life. Instead, you should get retested (with a PCR swab) within a few days (especially if you develop symptoms), and you should quarantine for 14 days.
On the other hand, if you got a test for no particular reason and it’s negative, then it’s probably safe to go on about your business while taking the usual precautions: wear a mask, social distance, and wash your hands frequently.