Table 2. Comparison of the most widely used ctDNA testing methodologies.

Test	Detection limit	Advantages	Disadvantages
Allele-specific PCR	0.1–1%	Easy to set-up	Detection of small number of alterations per sample
		Short time to result	Lower sensitivity
		FDA approved/CE-IVD kits available
		Specific equipment not always required
		Low cost
Digital PCR	0.01–0.1% (49,50)	High sensitivity	Detection of small number of alterations per sample
		Short time to result	Dedicated equipment necessary
		Low cost of reagents
		Absolute quantification (copies/mL)
NGS	0.01–2%	Large coverage	Reagents more expensive
		High sensitivity (if deep sequencing methods are used)	Dedicated equipment necessary
			Longer turn-around time
			Relative quantification (allelic fraction)

NGS, next generation sequencing.