Reverse-transcriptase PCR (RT-PCR) is a PCR sub-type that generates cDNA from template mRNA molecules. RT-PCR can detect and quantify RNA viruses. The first step in RT-PCR analysis is reverse transcribing the mRNA template using reverse transcriptase enzyme. This cDNA is then amplified using PCR. RT-PCR is a sensitive and accurate technique to detect RNA viruses present at very low levels.
qPCR can measure gene expression on its own. In gene expression analysis, a section of DNA is read to synthesize the mRNA, which then produces the protein of interest. However, in RT-PCR, reverse transcriptase creates cDNA, which is then used in PCR to calculate the mRNA transcripts.