Table 1.

Cell-free DNA forms and modifications used in clinical trials.

Cell-Free DNA	Abbreviation	Application
Total cfDNA	cfDNA, ccfDNA	General marker of physiological well-being, elevated in sepsis or under stress, temporarily increases during exercise
Circulating cell-free DNA
Serum/Plasma cell-free DNA
Circulating free DNA
Tumoral plasma DNA	ctDNA	Used in cancer therapy management, marker of cancer relapse or metastasis
(Circulating tumoral DNA)
Donor Derived cell-free DNA	dd-cfDNA	Used in detection of allograft rejection in transplantation
(Donor specific cell-free DNA)	dscfDNA
cell-free fetal DNA	cff-DNA	Used in non-invasive prenatal diagnostics, usually aneuploidy
circulating cell-free fetal DNA	ccff-DNA
Mitochondrial cfDNA	cf mtDNA	Releases during mitochondrial dysfunction, elevated under physiological stress or in some cancers
Circulating mitochondrial DNA
Methylated cell-free DNA	m-cfDNA	Mostly applied in oncology as a marker for cancer screening. Could be done specifically for a selected gene or globally
cfDNA integrity index	cfDI	Allows to distinguish if cfDNA is released from apoptotic or necrotic cells