When symptoms suggest an illness, particularly COVID-19, understanding when to test is crucial. Proper timing significantly influences test accuracy, guiding personal health decisions and limiting community spread.
Optimal Timing for Testing
Testing too early after symptoms begin can result in a false negative, especially with rapid antigen tests, as the viral load may not be high enough for detection. For rapid antigen tests, wait at least 24 to 48 hours after symptoms first arise to use the test for COVID-19. This allows the virus to replicate to a detectable level. If you have symptoms, a positive rapid antigen test is highly reliable.
Conversely, if symptoms are present, a PCR test can be taken as soon as possible. These tests are more sensitive, detecting the virus earlier than rapid antigen tests, and are considered the gold standard for accuracy. If your initial rapid test is negative, repeat the test 48 hours later. This strategy helps catch infections missed due to low viral load in early stages.
Interpreting Your Test Results
A positive COVID-19 test indicates the virus’s presence. For rapid antigen tests, even a faint line means SARS-CoV-2 antigens were detected. While rapid tests are accurate for positive results, they can sometimes remain positive longer than PCR tests due to persistent viral shedding, even after symptoms resolve.
A negative rapid antigen test, especially with symptoms, does not always definitively rule out infection. This can occur if the test was taken too early when viral concentration was low, leading to a false negative. If symptoms persist after a negative rapid test, retest after 24 to 48 hours. For persistent symptoms and negative rapid tests, a more sensitive PCR test may be considered for confirmation.
Next Steps After Testing
Following a positive COVID-19 test, recommendations include staying home and away from others if symptoms are present. You can typically return to regular activities once fever-free for at least 24 hours without fever-reducing medication and your other symptoms are improving. Take extra precautions for five days after returning, such as wearing a well-fitting mask around others.
If you test negative but still have symptoms, continue monitoring your health. Your symptoms might be due to another respiratory illness, like the flu or a common cold. Staying home until symptoms improve helps prevent the spread of any potential illness. Regardless of test results, seek medical advice if symptoms worsen, become severe, or if you are at higher risk for severe illness, such as being over 50 or having underlying health conditions.