Degradation of methylation signals in cryopreserved DNA

Clinical Epigenetics

Table 1 Subject and sample characteristics of the discovery and validation cohorts

	Discovery (n = 126)	Validation (n = 136)
Subject characteristics
Median age, years (range)	48.0 (38.1–71.5)	34.6 (19.0–44.7)
Self-reported ethnicity
Chinese	126 (100%)	136 (100%)
DNA sample characteristics
Median storage duration as blood	≤ 2 hours^a	≤ 5 days^b
Median storage duration as buffy coat at − 20 °C, days (range)	20 (1–77)	N/A^c
Median storage duration as DNA at − 20 °C, months (range)	44.4 (33.5–50.1)	21 (15.0–38.0)^d

^aBuffy coats were isolated from discovery cohort blood samples within two hours
^bNo detailed information is available for the duration of storage as blood for the validation cohort, except that all blood samples were extracted for DNA within five days
^cDNA was extracted directly from whole blood using an automated system
^dFor the validation cohort only, this duration includes initial storage at 4°C for up to two months

ISSN: 1868-7083