Cells in the tumor not only reproduce, but also decay. Decay products, including DNA, enter the bloodstream. Using the ARNA-BCA reagent kit in blood plasma, the content of DNA fragments of six genes is analyzed by the PCR-PB method (real-time polypeptide reaction).
Amplification of DNA fragments is carried out in real time using fluorescently-labeled DNA probes, each containing a fluorophore FAM at the 5′-end of the oligonucleotide and a “BHQ” suppressor at the 3′-end. Amplification is accompanied by destruction of the DNA probe by the exonuclease activity of Taq polymerase and an increase in the total fluorescence of the PCR mixture. The detection of accumulation of the PCR product occurs in each cycle in accordance with the increase in fluorescence of the fluorophore in the reaction, which is fixed by the detector of the device.