title: Validating laboratory results in a national observational cohort study without field centers: the Reasons for Geographic and Racial Differences in Stroke cohort.
abstract: OBJECTIVE
  The REasons for Geographic and Racial Differences in Stroke (REGARDS) study is a prospective cohort of 30,239 Americans in the contiguous United States; the first of this scale to use home visits to obtain, process, and ship biologic samples to a core laboratory. Pre-analytical factors resulting from this study design may affect the results of some laboratory assays. We investigated the impact of REGARDS processing on a variety of analytes.
  
  
  METHODS
  In REGARDS, blood samples were processed in the field by technicians who were trained on standardized methods for phlebotomy and sample processing. Field processing included centrifugation using varying non-uniform equipment and shipping overnight on ice to the University of Vermont, where samples were re-centrifuged for 30,000 ×g-minutes and stored at -80 °C. We assessed the effects of REGARDS sample handling by processing split samples from 20 volunteers using either ideal procedures or simulated REGARDS procedures. Assays for 19 analytes for potential study in REGARDS were then run on both samples and results compared.
  
  
  RESULTS
  Spearman correlation coefficients for analytes measured in ideal versus REGARDS processed samples ranged from 0.11 to 1.0. Thirteen of 19 analytes were highly correlated (>0.75), but platelet proteins were more variable.
  
  
  CONCLUSIONS
  Simulation of non-optimal field processing and shipment to a central laboratory showed high variability in analytes released by platelets. The majority of other analytes produced valid results, but platelet contamination in REGARDS samples makes measurement of platelet proteins unadvisable in these samples. Future analytes considered by REGARDS or similar studies should undergo similar pilot testing.
authors.affiliation: Department of Medicine, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: Gillett
authors.affiliation: Department of Pathology, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA.
authors.forename: Rebekah H
authors.initials: RH
authors.lastname: Boyle
authors.affiliation: Department of Medicine, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA; Department of Pathology, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA.
authors.forename: Neil A
authors.initials: NA
authors.lastname: Zakai
authors.affiliation: University of Alabama at Birmingham, 1665 University Blvd., Birmingham, AL 35233, USA.
authors.forename: Leslie A
authors.initials: LA
authors.lastname: McClure
authors.affiliation: Department of Pathology, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA.
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Jenny
authors.affiliation: Department of Medicine, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA; Department of Pathology, University of Vermont College of Medicine, 208 South Park Dr., Colchester, VT 05446, USA. Electronic address: mary.cushman@uvm.edu.
authors.forename: Mary
authors.initials: M
authors.lastname: Cushman
mesh_terms: D001800:Blood Specimen Collection / Q000379:methods / Q000592:standards*; D015331:Cohort Studies; D006801:Humans; D013048:Specimen Handling / Q000379:methods / Q000592:standards; D020521:Stroke / Q000097:blood / Q000175:diagnosis; D014481:United States
keywords: Biological markers; Blood chemical analysis; Blood specimen collection; Cohort studies; Quality control