Table 1.

Comparison of various types of cell-free DNA.

Sr number	Properties	Circulating Tumor DNA	Cell-Free Fetal DNA	Cell-Free Mitochondrial DNA
1	Strands	Single or double	Single or double	Double
2	Origin	Tumor cells	Trophoblastic cells [13]	Mitochondria or unknown [17]
3	Size	Less than 100 bp [18]	200 bp with dominate peaks at 162 bp [19]	Shorter fragment = less than 1 kb; larger fragments = 21 kb [14]
4	Applications	Early cancer detection, mutation analysis, cancer prediction, noninvasive cancer detection	Prenatal testing, genetic disease detection in the fetus	Forensic sciences, detection of the geographical distribution of genes, gene flow identification, human remain recognition, cancer detection
5	Advantages	Sensitive than other cancer detection techniques, can detect mutations better than biopsy, detect heterogeneous tumor cells, predict cancer reoccurrence	Increased chances to detect chromosomal disorders, noninvasive, no side effects	Lacks genetic ambiguities, higher copy number, a diagnostic and prognostic marker for multiple diseases
6	Disadvantages	Cannot be detected by FISH or ICC techniques, expensive, lack standardization	Increased chances of false positives or false negatives	No heterogenicity, lower discrimination power