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eISSN 2234-3814

Table. 3. Table 3

Recommendations for pre-analytical procedures

Recommendation	Grade of recommendation	Level of evidence
It is recommended to use plasma rather than serum for ctDNA analysis.	A	I
It is recommended to separate plasma immediately when collecting blood in an EDTA tube and not delay plasma separation more than 4–6 hrs.	A	I
It may be considered to use cell preservation tubes if plasma separation is delayed more than 4–6 hrs.	B	I
It may be considered to avoid agitation and temperature fluctuation when transporting samples to the laboratory.	B	I
It may be considered to conduct two-step centrifugation for plasma isolation.	B	I
It is recommended to avoid buffy coat contamination when separating plasma.	A	I
It is recommended to analyze cfDNA in terms of quantity and quality before downstream analysis.	A	I
For long-term storage, it may be considered to store plasma or cfDNA extracts at −80°C and in aliquots to avoid repeated freeze–thaw cycles.	B	I

Abbreviations: ctDNA, circulating tumor DNA; cfDNA, cell-free DNA.