A friend recently shared his and his partner’s COVID story. They were both fully vaccinated and masked in public settings, but when his partner discovered he had been exposed to a positive case, he got a rapid test that day which came back negative. He also took a PCR---polymerase chain reaction--- test that day and got the results five days later: negative. Two weeks later, he lost his sense of smell. He got another rapid test and it was positive. My friend then began developing symptoms and waited 4 days after his symptoms started to get rapid tested, and also received a positive result.
Hello, I’m Dr. Brooke Hildebrand Clubbs at Southeast Missouri State University. My friend’s story brings up important issues regarding types of tests and timing.
First, there are three types of tests.The first one, the PCR test, identifies whether the actual COVID virus genetic material exists by taking a sample via a nasal pharyngeal swab. The second one, the antigen test, also known as the rapid test, is also done by nasal swab. It detects the outer protein of the virus. The third type, an antibody test, is a blood test that looks for whether the individual has mounted an immune response.
As for timing, in many cases, a person with the virus would test positive for COVID around 3-5 days after contracting it. Thus, getting tested the day after a potential exposure means you’ll have a very high chance of a negative test result even if you have been infected.Tests are most accurate three days after symptom onset. However, the CDC notes the incubation period could be anywhere from 2 to 14 days.
Resources:
https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html
https://www.idsociety.org/covid-19-real-time-learning-network/diagnostics/rapid-testing/
https://health.clevelandclinic.org/when-to-get-tested-for-covid/
https://medical.mit.edu/covid-19-updates/2020/07/when-should-i-be-tested