Under what circumstances might a SARS-COV-2 antigen test kit produce a false negative result?

SARS-COV-2 antigen test kits may produce false negative results under the following circumstances:

Improper sampling is a common cause of false negative results. When collecting a sample, if the swab does not go deep enough, or if too small a sample is collected, there may not be enough viral antigens in the sample to be detected. This often occurs in the context of self-sampling, as non-experts may not be familiar with proper sampling techniques. In addition, if oral or nasal secretions are diluted during sampling, for example by drinking water or gargling, the concentration of viral antigens in the sample may be too low, resulting in false negative results.

Low viral load can also affect the accuracy of antigen testing. In the early stages of infection, the viral load may not yet reach detectable levels, or in some patients with mild illness or asymptomatic infection, the viral load may remain at a low level. In this case, the antigen test may not capture enough viral antigen, resulting in a false negative result.

Quality issues with the kit itself are also an important factor leading to false negative results. If the kit is expired, improperly stored, or contaminated, the antibodies or enzymes in the reagent may lose activity or produce non-specific reactions, affecting the accuracy of the test results. Therefore, when using antigen detection kits, you should ensure that they are of reliable quality and used within the validity period.

Operational errors may also lead to false negative results. Antigen detection kits usually need to be operated according to specific steps and conditions. If the operator does not read the instructions carefully or fails to operate in accordance with the requirements, it may lead to deviations in the test results. For example, if the reagents are not mixed with the sample for insufficient or too long, or if the lighting conditions are poor when the results are read, the accuracy of the results may be affected.