The importance of careful blood processing in isolation of cell-free DNA.

In healthy individuals, the source of cell-free plasma DNA is predominantly apoptotic, whereas, increased plasma DNA integrity is seen in cancer patients. Therefore, it is important to carefully isolate absolutely "cell-free" plasma DNA. Plasma DNA from 30 healthy females was analyzed using 4 PCR amplicons of increasing size, comparing standard blood processing with additional centrifugation steps prior to DNA extraction. Cellular DNA contamination, indicated by positive amplicons >300 bp was eliminated only after the extra centrifugation step. This highlights the importance of careful processing in preparation of cell-free plasma DNA as a tool for cancer detection and we recommend the use of a microcentrifuge spin, prior to DNA extraction.