At Summit Express Urgent Care, we use the Quidel Sofia2 machine to run a rapid SARS antigen test. Once your sample is collected, it will take 15 minutes to receive your results. Each sample is processed individually after being placed on a single use cartridge that is then inserted into the Sofia2 machine. It uses advanced fluorescence detection with an ultraviolet LED energy source to determine the presence or absence of COVID-19 antigens. There is no contact between your specimen and the machine itself; therefore, there is no cross-contamination. The specificity of the test approaches 99% which means that there is only a 1% chance that your result is a false positive. The sensitivity approaches 97% which means that the chances of you receiving a false negative is around 3%. (These numbers are from a controlled study run by the Quidel corporation).
The PCR test, which is processed by commercial laboratories, checks for COVID-19 DNA. It is considered to be a more accurate test. However, no test is perfect. If the sample collection is not done properly, it can yield a false negative result. The swab should be inserted at least three inches into the nostrils. If you are not uncomfortable during the test, it has not been done properly.