title: The effects of freeze-thaw on β-trace protein and β2-microglobulin assays after long-term sample storage.
abstract: OBJECTIVE
  To evaluate the effect of a freeze-thaw cycle on β-trace protein (βTP) and β2-microglobulin (β2M).
  
  
  METHODS
  We compared βTP and β2M concentrations before and after a single freeze-thaw cycle in long-term stored samples from 172 participants of the Third National Health and Nutrition Examination Survey (NHANES III).
  
  
  RESULTS
  Measurements of βTP and β2M before and after freeze-thaw were highly correlated with Spearman's coefficients of 0.90 and 0.99, respectively. Serum concentrations of βTP were slightly lower after freeze-thaw (-0.05 mg/L, P=0.006). Measurements of β2M did not differ before and after freeze-thaw (P=0.35).
  
  
  CONCLUSIONS
  βTP and β2M measurements were robust to a single freeze-thaw cycle, although β2M appeared more stable than βTP. These results have implications for future studies of these biomarkers.
authors.affiliation: Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins Medical Institutions, Baltimore, MD, USA.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Juraschek
authors.forename: Josef
authors.initials: J
authors.lastname: Coresh
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Inker
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Rynders
authors.forename: John H
authors.initials: JH
authors.lastname: Eckfeldt
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Selvin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001800:Blood Specimen Collection; D015925:Cryopreservation; D005615:Freezing; D006801:Humans; D019746:Intramolecular Oxidoreductases / Q000097:blood*; D054834:Lipocalins / Q000097:blood*; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors; D001613:beta 2-Microglobulin / Q000097:blood*
chemical_list: D015415:Biomarkers; D054834:Lipocalins; D001613:beta 2-Microglobulin; D019746:Intramolecular Oxidoreductases; C022466:prostaglandin R2 D-isomerase