title: Perfluoroalkyl Acid Concentrations in Blood Samples Subjected to Transportation and Processing Delay.
abstract: BACKGROUND
  In studies of perfluoroalkyl acids, the validity and comparability of measured concentrations may be affected by differences in the handling of biospecimens. We aimed to investigate whether measured plasma levels of perfluoroalkyl acids differed between blood samples subjected to delay and transportation prior to processing and samples with immediate processing and freezing.
  
  
  METHODS
  Pregnant women recruited at Aarhus University Hospital, Denmark, (n = 88) provided paired blood samples. For each pair of samples, one was immediately processed and plasma was frozen, and the other was delayed and transported as whole blood before processing and freezing of plasma (similar to the Danish National Birth Cohort). We measured 12 perfluoroalkyl acids and present results for compounds with more than 50% of samples above the lower limit of quantification.
  
  
  RESULTS
  For samples taken in the winter, relative differences between the paired samples ranged between -77 and +38% for individual perfluoroalkyl acids. In most cases concentrations were lower in the delayed and transported samples, e.g. the relative difference was -29% (95% confidence interval -30; -27) for perfluorooctane sulfonate. For perfluorooctanoate there was no difference between the two setups [corresponding estimate 1% (0, 3)]. Differences were negligible in the summer for all compounds.
  
  
  CONCLUSIONS
  Transport of blood samples and processing delay, similar to conditions applied in some large, population-based studies, may affect measured perfluoroalkyl acid concentrations, mainly when outdoor temperatures are low. Attention to processing conditions is needed in studies of perfluoroalkyl acid exposure in humans.
authors.affiliation: Perinatal Epidemiology Research Unit, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Cathrine Carlsen
authors.initials: CC
authors.lastname: Bach
authors.affiliation: Perinatal Epidemiology Research Unit, Aarhus University Hospital, Aarhus, Denmark; Department of Pediatrics, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Tine Brink
authors.initials: TB
authors.lastname: Henriksen
authors.affiliation: Department of Environmental Science, Aarhus University, Roskilde, Denmark.
authors.forename: Rossana
authors.initials: R
authors.lastname: Bossi
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark.
authors.forename: Bodil Hammer
authors.initials: BH
authors.lastname: Bech
authors.affiliation: Department of Obstetrics and Gynecology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Fuglsang
authors.affiliation: Section for Epidemiology, Department of Public Health, Aarhus University, Aarhus, Denmark; Department of Epidemiology, Fielding School of Public Health, University of California Los Angeles, California, United States of America.
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Research Unit for Obstetrics and Gynecology, Institute of Clinical Research, University of Southern Denmark, Odense, Denmark.
authors.forename: Ellen Aagaard
authors.initials: EA
authors.lastname: Nohr
mesh_terms: D000328:Adult; D017738:Alkanesulfonic Acids / Q000097:blood*; D002210:Caprylates / Q000097:blood*; D002853:Chromatography, Liquid; D005260:Female; D005466:Fluorocarbons / Q000097:blood*; D006801:Humans; D011247:Pregnancy; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods; D053719:Tandem Mass Spectrometry
chemical_list: D017738:Alkanesulfonic Acids; D002210:Caprylates; D005466:Fluorocarbons; C023036:perfluorooctanoic acid; C076994:perfluorooctane sulfonic acid