Besides issues with reproducibility, qPCR reactions can also be affected by nucleic acid contamination, leading to false positive results.
The three possible sources of contamination are:
- cross-contamination between samples
- contamination from laboratory equipment and
- carryover contamination by amplified products from previous qPCRs.
Precautions can be taken to reduce the risk of contamination: uracil DNA glycosylase (UDG) can be used to prevent DNA carryover contamination between reactions, materials can be systematically decontaminated, and separate workstations for each step of the qPCR process can be designated to create an efficient workflow. However, those measures do not eliminate the major cause of false positive results: the accidental contamination with positive samples during Liquid Handling.