The chances of false positives in antigen test kits are not high, as long as the quality of the kits is correct and the operation is standardized, false negatives usually do not occur.
Antigen test kits are mainly based on the specific binding of antigen and antibody. If there is one line on the test strip, the result is negative. If it shows two lines, then it is positive.
When a person is first infected with a virus, the antigen test kit will have a lower positive rate because the viral load is relatively low, and false negatives may occur. As time goes by, the viral load gradually rises, and then the positive rate of antigen detection can be increased dramatically, and the detection rate can reach more than 90%.
In addition, if the antigen test is performed one week after the virus has been infected, the positivity rate decreases dramatically because the viral load is lower at this time, and the sensitivity of the antigen test kit decreases, resulting in false negatives.
The antigen test needs to be positive when the infected person is highly infectious and carries a large amount of virus. It is generally more sensitive from day 3 to day 7 of infection with the new coronavirus and is more suitable for use in people in the first week of illness. Therefore, antigen testing can only be used as a supplement to nucleic acid testing, complementing nucleic acid testing and diverting some of the low-risk population from the need for nucleic acid testing.