These diagnostic tests are considered the most sensitive for detecting an active infection, and the results are highly accurate. A fluid sample is collected by inserting a long nasal swab into your nostril or into your throat. RT–PCR is a variation of PCR, or polymerase chain reaction. The two techniques use the same process except that RT–PCR has an added step of reverse transcription of RNA to DNA, or RT, to allow for amplification.These diagnostic tests are considered the most sensitive for detecting an active infection, and the results are highly accurate.