title: Stability of plasma adrenocorticotrophic hormone (ACTH): influence of hemolysis, rapid chilling, time, and the addition of a maleimide.
abstract: OBJECTIVE
  The aim of this study was to examine the effects of hemolysis, rapid chilling, time, and the addition of a maleimide on the stability of human plasma ACTH measurements.
  
  
  METHODS
  Partially hemolyzed EDTA blood (n=10), initially at 37°C, was centrifuged at 4°C either immediately or after rapid chilling in ice/water. Plasma ACTH was then measured either immediately, or after 1h at 22°C with or without the addition of 2mM N-phenyl maleimide (NPM).
  
  
  RESULTS
  For 0.2% hemolysis compared to no hemolysis, the mean (±SEM) loss with immediate centrifugation and immediate ACTH measurement was 11±1%. This loss was significantly (p<0.002) reduced to 6±1% by an initial rapid chilling of the samples. For analysis after 1h at 22°C, the addition of NPM decreased the loss of ACTH from 15±2% to 2±2% (p<0.002).
  
  
  CONCLUSIONS
  Rapid chilling, prompt analysis, and addition of NPM can each reduce the interference of hemolysis in the measurement of plasma ACTH concentrations.
authors.affiliation: Endolab, Canterbury Health Laboratories, Christchurch Hospital, New Zealand. john.livesey@cdhb.govt.nz
authors.forename: John H
authors.initials: JH
authors.lastname: Livesey
authors.forename: Barbara
authors.initials: B
authors.lastname: Dolamore
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood*; D015925:Cryopreservation; D005260:Female; D006461:Hemolysis; D006801:Humans; D008297:Male; D008301:Maleimides / Q000737:chemistry*; D011309:Preservation, Biological / Q000379:methods*; D013997:Time Factors
chemical_list: D008301:Maleimides; C043592:maleimide; D000324:Adrenocorticotropic Hormone