A PCR test is the gold standard in COVID-19 testing. It offers the most accurate results as it can detect even the smallest amount of virus. This means that a negative PCR test result provides the most reliable indication you can safely continue to work and travel.
Not all PCR tests are equivalent. The DHSC requirements for Day 2 arrival PCR test are different from other PCR tests such as PCR Fit to Fly. PCR is a methodology that uses assay reagents which can have very different performance characteristics such as sensitivity, specificity or limit of detection. It could target one or multiple genes for example. It might also need different buffer (liquid) used for the sample collection (when customers are swabbed) to ensure that all the tests required by DHSC (such as sequencing for the identification of variants of concern for positive Day 2 samples) can be carried out.
Lateral flow is an established technology, adapted to detect antigens that are present when a person has COVID-19. The best-known example of a lateral flow test is the home pregnancy test kit.
The test kit is a hand-held device with an absorbent pad at one end and a reading window at the other. Inside the device is a strip of test paper that changes colour in the presence of COVID-19 antigens.
A negative result means that active coronavirus infection was not detected, at the time of the test. However, this does not guarantee that you do not have coronavirus. It is not analysed in a laboratory, like the PCR tests are.