Circulating nucleic acids in plasma and serum: recent developments.
Nucleic acids (DNA and RNA) have been detected in plasma, serum, urine, and other body fluids from healthy subjects as well as in patients. The ability to detect and quantitate specific DNA and RNA sequences has opened up the possibility of diagnosis and monitoring of diseases. With the recent developments in the field of circulating nucleic acids the application in the diagnostic field has increased. The recent discovery of epigenetic changes in placental/fetal DNA and the detection of fetal/placental-specific RNAs have made it possible to use this technology in all pregnancies irrespective of the gender of the fetus. With the application of mass spectrometry and other techniques to this field, it is now possible to detect very small amounts of specific DNA in the presence of excess of other nonspecific nucleic acids (e.g., detection of mutations in fetal DNA in the presence of excess of maternal DNA). Circulating nucleic acids have now been shown to be useful in other conditions, such as diabetes mellitus, trauma, stroke, and myocardial infarction. In oncology, detection and monitoring of tumors is now possible by the detection of tumor-derived nucleic acids. In spite of these advances questions regarding the origin and biologic significance of circulating nucleic acids remain to be answered. Furthermore pre-analytical and analytical aspects of this field remain to be standardized.