Storage Conditions for Blood Samples, for Later Analysis in Criminal Prosecution

Abstract

Backround: Aim of this study was to demonstrate the stability of blood–ethanol concentration over a storage period. The precise storage time during which ethanol can be reliably measured in frozen blood samples is unknown. Materials and Methods: In study A, samples were thawed and reanalyzed for ethanol content; their storage time since the first analysis ranged from one to 295 days. The percent difference between the first and second ethanol measurements was calculated as lost ethanol (%). For study B, the ethanol concentrations of 34 samples were measured within 180 days of, and at a randomly selected interval from, the working day. Results: In study A, the calculated lost ethanol values ranged from 1% to 30%. There was no correlation between the calculated ethanol values and the measures on the second ethanol analysis day. A significant difference was detected between the two analyses in study B (p: 0.01). Conclusions: It was concluded that blood samples to be analyzed for ethanol concentration can be stored at –80°C for many months, with no loss of concentration provided that analysis is undertaken as promptly as possible and blood samples are frozen as soon after collection as possible.