title: High-quality and -quantity DNA extraction from frozen archival blood clots for genotyping of single-nucleotide polymorphisms.
abstract: BACKGROUND
  The recovery of biological samples for genetic epidemiological studies can be cumbersome. Blood clots are routinely collected for serological examinations. However, the extraction of DNA from blood clots can be difficult and often results in low yields.
  
  
  OBJECTIVE
  The aim was to compare the efficiency of commercial purification kits for extracting DNA from long-term frozen clotted blood.
  
  
  METHODS
  Serum tubes with clotted blood were stored at -20°C for 1 to 2.5 years before DNA extraction. DNA was extracted from 10 blood clot samples using PureGene (Qiagen) with and without glycogen, the QIAamp DNA Micro kit (Qiagen), and the Nucleospin 96 Blood kit (Macherey-Nagel). Furthermore, blood clots from 1055 inflammatory bowel disease patients were purified using the Maxwell 16 Blood purification kit (Promega). The DNA was extracted according to the manufacturers` instructions and real-time PCR and the A(260)/A(280) ratio were used to evaluate the quality of the extracted DNA.
  
  
  RESULTS
  The highest DNA yield was obtained by the Maxwell 16 Blood purification kit (Promega) with a median of 4.90 μg (range 0.8-25 μg) pr 300 μL total blood. PureGene with glycogen (Qiagen) had the second highest yield with a median of 0.65 μg (range 0.5-2.6 μg) pr 300 μL total blood.
  
  
  CONCLUSIONS
  The yield obtained by the different commercial kits varied considerably. Our work demonstrates that high-quality and -quantity DNA can be extracted with the Maxwell 16 Blood purification kit (Promega) from cryopreserved blood clots, even after prolonged storage. The recovered DNA served as a reliable PCR template for single-nucleotide polymorphism assays.
authors.affiliation: Medical Department, Viborg Regional Hospital, Viborg, Denmark. stb@mb.au.dk
authors.forename: Steffen
authors.initials: S
authors.lastname: Bank
authors.forename: Bjørn Andersen
authors.initials: BA
authors.lastname: Nexø
authors.forename: Vibeke
authors.initials: V
authors.lastname: Andersen
authors.forename: Ulla
authors.initials: U
authors.lastname: Vogel
authors.forename: Paal Skytt
authors.initials: PS
authors.lastname: Andersen
mesh_terms: D004247:DNA / Q000097:blood* / Q000302:isolation & purification*; D005615:Freezing; D005838:Genotype; D060005:Genotyping Techniques; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods; D020641:Polymorphism, Single Nucleotide
chemical_list: D004247:DNA