title: Stability of plasma analytes after delayed separation of whole blood: implications for epidemiological studies.
abstract: BACKGROUND
  Large blood-based epidemiological studies require simple, cost-effective sample collection methods. Immediate sample separation or rapid transport of chilled blood samples to a central laboratory may be impractical or prohibitively expensive. To assess the feasibility and reliability of transporting blood samples over several days at ambient temperature (e.g. by mail), we evaluated the stability of various plasma analytes in samples stored at room temperature or chilled.
  
  
  METHODS
  Multiple vacutainers of blood, containing EDTA and aprotinin as preservative, were drawn from 12 volunteers and stored at 21 degrees C or 4 degrees C. Immediately after collection and 1, 2, 3, 4, and 7 days later, vacutainers stored at each temperature were centrifuged, and the plasma was aliquoted and stored at -80 degrees C. Subsequently, all aliquots from each individual were analysed in one analytical run for a range of chemistries.
  
  
  RESULTS
  In whole blood stored at room temperature for up to 7 days, concentrations of albumin, apolipoproteins A1 and B (apoA1 and apoB), cholesterol, high density lipoprotein (HDL), total protein, and triglycerides changed by less than 4%, and low density lipoprotein (LDL) by less than 7%. Whilst alanine transaminase (ALT), creatine kinase (CK), creatinine, and gamma-glutamyl transferase (GGT) concentrations changed substantially at room temperature, there was less than 4% change during chilled storage up to 7 days. By contrast, aspartate transaminase (AST) concentrations increased markedly under both conditions.
  
  
  CONCLUSIONS
  A wide range of important analytes, including lipids, change by only a few per cent in whole blood during storage at room temperature for several days. Mailed transport of whole blood samples may, therefore, be a simple and cost-effective option for large-scale epidemiological studies.
authors.affiliation: Clinical Trial Service Unit & Epidemiological Studies Unit, Nuffield Department of Clinical Medicine, University of Oxford, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Clark
authors.forename: Linda D
authors.initials: LD
authors.lastname: Youngman
authors.forename: Alison
authors.initials: A
authors.lastname: Palmer
authors.forename: Sarah
authors.initials: S
authors.lastname: Parish
authors.forename: Richard
authors.initials: R
authors.lastname: Peto
authors.forename: Rory
authors.initials: R
authors.lastname: Collins
mesh_terms: D000410:Alanine Transaminase / Q000097:blood; D001774:Blood Chemical Analysis; D001793:Blood Preservation / Q000379:methods; D001800:Blood Specimen Collection / Q000379:methods* / Q000592:standards; D002784:Cholesterol / Q000097:blood; D003402:Creatine Kinase / Q000097:blood; D003404:Creatinine / Q000097:blood; D015925:Cryopreservation; D004812:Epidemiologic Methods; D005240:Feasibility Studies; D006801:Humans; D008074:Lipoproteins / Q000097:blood; D012680:Sensitivity and Specificity; D012709:Serum Albumin / Q000032:analysis; D013997:Time Factors; D014280:Triglycerides / Q000097:blood; D005723:gamma-Glutamyltransferase / Q000097:blood
chemical_list: D008074:Lipoproteins; D012709:Serum Albumin; D014280:Triglycerides; D002784:Cholesterol; D003404:Creatinine; D005723:gamma-Glutamyltransferase; D000410:Alanine Transaminase; D003402:Creatine Kinase