Why are some COVID test results false positive?

RT-PCR tests are used for the detection of COVID-19 and have an
accuracy of 96%. These tests are highly sensitive and specific. If a person is infected
with COVID, the test result will come back positive. But there is a small
chance for a person’s result to come back positive even though the person is
not infected. This type of test result is called a false positive.

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How are the samples tested?

Chemicals are used to extract the RNA from the sample which
are taken from the nose and throat swabs. With the help of some special
fluorescent dye, the laboratories, identify the sample to be positive or
negative based on the brightness of the fluorescence

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What are the reasons for false positives?

The reasons for a false positive are laboratory error and
wrong cross reaction. Clerical error, testing wrong sample, contamination of
sample or chemical issues are the laboratory errors due to which a result might
show a false positive. For every 100,000 people who have been tested positive, 4,000
false positives can be expected.