title: Buffy coat specimens remain viable as a DNA source for highly multiplexed genome-wide genetic tests after long term storage.
abstract: BACKGROUND
  Blood specimen collection at an early study visit is often included in observational studies or clinical trials for analysis of secondary outcome biomarkers. A common protocol is to store buffy coat specimens for future DNA isolation and these may remain in frozen storage for many years. It is uncertain if the DNA remains suitable for modern genome wide association (GWA) genotyping.
  
  
  METHODS
  We isolated DNA from 120 Action to Control Cardiovascular Risk in Diabetes (ACCORD) clinical trial buffy coats sampling a range of storage times up to 9 years and other factors that could influence DNA yield. We performed TaqMan SNP and GWA genotyping to test whether the DNA retained integrity for high quality genetic analysis.
  
  
  RESULTS
  We tested two QIAGEN automated protocols for DNA isolation, preferring the Compromised Blood Protocol despite similar yields. We isolated DNA from all 120 specimens (yield range 1.1-312 ug per 8.5 ml ACD tube of whole blood) with only 3/120 samples yielding < 10 ug DNA. Age of participant at blood draw was negatively associated with yield (mean change -2.1 ug/year). DNA quality was very good based on gel electrophoresis QC, TaqMan genotyping of 6 SNPs (genotyping no-call rate 1.1% in 702 genotypes), and excellent quality GWA genotyping data (maximum per sample genotype missing rate 0.64%).
  
  
  CONCLUSIONS
  When collected as a long term clinical trial or biobank specimen for DNA, buffy coats can be stored for up to 9 years in a -80°C frozen state and still produce high yields of DNA suitable for GWA analysis and other genetic testing.
authors.affiliation: Center for Public Health Genomics, University of Virginia, Charlottesville, VA, USA. jcm6t@virginia.edu
authors.forename: Josyf C
authors.initials: JC
authors.lastname: Mychaleckyj
authors.forename: Emily A
authors.initials: EA
authors.lastname: Farber
authors.forename: Jessica
authors.initials: J
authors.lastname: Chmielewski
authors.forename: Jamie
authors.initials: J
authors.lastname: Artale
authors.forename: Laney S
authors.initials: LS
authors.lastname: Light
authors.forename: Donald W
authors.initials: DW
authors.lastname: Bowden
authors.forename: Xuanlin
authors.initials: X
authors.lastname: Hou
authors.forename: Santica M
authors.initials: SM
authors.lastname: Marcovina
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D058621:Blood Buffy Coat / Q000378:metabolism*; D001800:Blood Specimen Collection / Q000379:methods*; D004247:DNA / Q000235:genetics*; D005260:Female; D005820:Genetic Testing; D015894:Genome, Human / Q000235:genetics*; D055106:Genome-Wide Association Study; D005838:Genotype; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011786:Quality Control; D013997:Time Factors; D014021:Tissue Preservation / Q000379:methods*
chemical_list: D004247:DNA