The RT-PCR test works by identifying the RNA traces of the coronavirus through a swab sample taken from a person’s nose or throat. However, false negatives can occur at about 30 per cent of the time, as there are a lot of stages during the collection of the sample, where contamination may lead to errors. Hence, even though it is one of the most sensitive tests for coronavirus testing, the RT-PCR (reverse-transcription PCR) has a sensitivity of about 70 per cent currently.
A false negative simply means that a person infected with COVID-19 has been missed by the test. If the swab sample is not taken correctly to conduct RT-PCR, it may lead to a false negative. Also, there could be a low viral load present in the throat when compared to the nasopharynx.
Hence, an incorrectly taken swab can miss the viral particles altogether, or even if the viral load is too less in the samples, the chances of false negative increases.