title: Comparison of blood ethanol stabilities in different storage periods.
abstract: BACKGROUND
  Measurements of blood ethanol concentrations must be accurate and reliable. The most important factors affecting blood ethanol stability are temperature and storage time. In this study, we aimed to compare ethanol stability in plasma samples at -20 °C for the different storage periods.
  
  
  METHODS
  Blood samples were collected from intoxicated drivers (N=80) and initial plasma ethanol concentrations were measured immediately. Plasma samples were then stored at -20 °C and re-assessed after 2, 3, 4, or 5 months of storage. Differences between the initial and stored ethanol concentrations in each group (N=20) were analyzed using Wilcoxon matched-pairs test. The deviation from the initial concentration was calculated and compared with Clinical Laboratory Improvement Amendments (CLIA'88) Proficiency Testing Limits. Relationships between the initial concentrations and deviations from initial concentrations were analyzed by Spearman's correlation analysis. For all statistical tests, differences with P values of less than 0.05 were considered statistically significant.
  
  
  RESULTS
  Statistically significant differences were observed between the initial and poststorage ethanol concentrations in the overall sample group (P<0.001). However, for the individual storage duration groups, analytically significant decreases were observed only for samples stored for 5 months, deviations from the initial concentrations exceeded the allowable total error (TEa). Ethanol decreases in the other groups did not exceed the TEa.
  
  
  CONCLUSIONS
  According to our results, plasma ethanol samples can be kept at -20 °C for up to 3-4 months until re-analysis. However, each laboratory should also establish its own work-flow rules and criterion for reliable ethanol measurement in forensic cases.
authors: Dumlupinar University, Faculty of Medicine, Department of Medical Biochemistry, Kutahya, Turkey.
authors: Fatma Emel
authors: FE
authors: Kocak
authors: Dumlupinar University, Evliya Celebi Education, and Research Hospital, Department of Medical Biochemistry, Kutahya, Turkey.
authors: Ozben Ozden
authors: OO
authors: Isiklar
authors: Dumlupinar University, Faculty of Medicine, Department of Medical Biochemistry, Kutahya, Turkey.
authors: Havva
authors: H
authors: Kocak
authors: Dumlupinar University, Evliya Celebi Education, and Research Hospital, Department of Medical Biochemistry, Kutahya, Turkey.
authors: Ayfer
authors: A
authors: Meral
mesh_terms: D000435:Alcoholic Intoxication / Q000097:blood*; D001334:Automobile Driving; D015925:Cryopreservation / Q000379:methods*; D000431:Ethanol / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D000431:Ethanol
keywords: ethanol; preanalytical phase; stability; storage temperature