Overview of circulating nucleic acids in plasma/serum

The existence of circulating nucleic acids in plasma and serum (CNAPS) was first described almost six decades ago. However, the prognostic and diagnostic utility of this circulating DNA/RNA has only really begun to be appreciated in the last decade. Earlier studies concentrated mainly on investigations concerned with fetal medicine and oncology, and significant progress was made in both specialities. More recently the field of enquiry has extended further, and attention has turned to other pathologic states, including trauma, sepsis, myocardial infarction, stroke, transplantation, diabetes mellitus, and hematologic disorders. In some of these studies, mitochondrial as well as genomic DNA and tissue-specific mRNA have been analyzed, either quantitatively or qualitatively or both, and have been shown to be modified in the presence of disease. While there is tremendous potential for CNAPS as a clinical modality, many of the emerging studies seem to be confined to a few dedicated labs. Therefore, additional independent studies are necessary in some cases in order to show reproducibility, which will further consolidate the field. Despite this shortcoming, and with the evidently increasing number of applications for CNAPS, it is highly likely that routine testing, as described, will become reality within the next 5 to 10 years.