Background: In the last ten years, researchers actively studied cell-free nucleic acids present in plasma or serum with great expectations as potential biomarkers for cancer and other pathologic conditions. In the present manuscript the main findings related to the principal characteristics of C-DNA and some methodological considerations on sample collection and extraction as well as on some innovative assay methods have been summarized.

Materials and Methods: We compares different commercial kits for C-DNA isolation based on two criteria: A) procedure for capturing DNA by column impacted with patented Polymers so called Cartridge based-DNA isolation; and B) procedure based on a simple digestion of the lysate cell mixture digest by proteinase K and subsequent precipitation of DNA salt.
The measure of the best methods was based on the quantification of DNA integrity, amplifying the human Telomerase Reverse Transcriptase (hTERT) in a subset of C-DNA of healthy donors.

Results: The assays differs significantly as regard to the target genes (hTERT) but shares on the use of a common forward primer and reverse primers delimitating amplicons.

Conclusions: Recent reports on the importance of circulating nucleic acids in the intercellular exchange of genetic information between eukaryotic cells have been reviewed.