title: The effect of storage temperature fluctuations on the stability of biochemical analytes in blood serum.
abstract: BACKGROUND
  Irreproducibility of scientific results constitutes an undesirably onerous economic burden and is in many cases caused by low-quality materials. Therefore, researchers are increasingly devoting their attention to the bioresources they use. In turn, those bioresources are required to validate their preanalytical processes in order to ensure best possible quality. The present study thus aimed to evaluate the impact of repeated temperature fluctuations, as they occur in most research biobanks due to repetitive opening and closing of freezer doors, on the stability of 26 biochemical analytes.
  
  
  METHODS
  Serum of 43 individuals was randomly assigned to a fluctuation (n=21) and a control group (n=22). Serum of the fluctuation group underwent controlled temperature fluctuations (30 fluctuations <-75°C - <-65°C - <-75°C under real-life freezer conditions within 21 days). Control sera were stored at constant conditions. After 10, 20, and 30 fluctuations, results derived from the fluctuation group were compared to baseline and to the control group by means of general linear models.
  
  
  RESULTS
  Sixteen biomarkers showed statistically significant changes over time, whereas only seven of those presented with diagnostically/clinically relevant changes at certain time points (aspartate aminotransferase, amylase, calcium, uric acid, creatinine, inorganic phosphate and total protein). However, there was no difference between the fluctuation and the control group.
  
  
  CONCLUSIONS
  Some serum analytes are influenced by storage, even at temperatures as low as <-70°C. In contrast, we found no evidence that complex temperature fluctuations produced by storage of and access to biospecimens in biobank freezers generate any additional variability.
authors.affiliation: .
authors.forename: Helmuth
authors.identifier: http://orcid.org/0000-0003-4605-2503
authors.initials: H
authors.lastname: Haslacher
authors.affiliation: .
authors.forename: Thomas
authors.initials: T
authors.lastname: Szekeres
authors.affiliation: .
authors.forename: Marlene
authors.initials: M
authors.lastname: Gerner
authors.affiliation: .
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Ponweiser
authors.affiliation: .
authors.forename: Manuela
authors.initials: M
authors.lastname: Repl
authors.affiliation: .
authors.forename: Oswald F
authors.initials: OF
authors.lastname: Wagner
authors.affiliation: .
authors.forename: Thomas
authors.initials: T
authors.lastname: Perkmann
mesh_terms: D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis; D001800:Blood Specimen Collection / Q000295:instrumentation / Q000379:methods*; D005615:Freezing; D006801:Humans; D013696:Temperature; D013997:Time Factors
chemical_list: D015415:Biomarkers
keywords: biobank; biochemical; clinical chemistry; storage; temperature fluctuations