Accuracy of rapid antigen tests for COVID-19

The main benefit of rapid antigen testing for COVID-19 is speed. Point-of-care antigen tests, such as the COVID-19 Antigen Rapid Test kit, can provide a coronavirus diagnosis in 15 minutes. However, there are concerns about the accuracy of the test, which we will analyze below.

1. False negative

False negatives are often what people refer to as "accuracy" when discussing a COVID-19 diagnostic test. False negatives can occur in both PCR and antigen tests. The main factor that determines whether a test is likely to have a false negative is its sensitivity: the amount of virus that needs to be present in order for the test to show a positive result.A study in the Annals of Internal Medicine showed that the rate of false-negative tests using rapid COVID-19 antigen test kits varied widely, depending on when the test was performed during the course of infection, as the viral load varied widely during infection. Studies have found that the false-negative rate can be as high as 100 percent in the four days before the onset of symptoms, while the false-negative rate never exceeds 20 percent after the onset of symptoms.

2. False positives

Another factor that affects the accuracy of a COVID-19 antigen test is a false positive, which is a situation in which a test result indicates infection when in fact there is no infection. There is no scientific reason why false positives should be a problem; If the virus particles are not present, the test should not give a positive result. This is largely true. Antigen tests rarely report false positives. In the event of a false positive, it is usually thought to be due to contamination caused by improper handling of the sample, rather than the test itself.