Testing antemortem blood samples for ethanol after four to seven years of refrigerated storage.

Abstract

The previous studies on ethanol stability in antemortem blood samples stored under various conditions have shown that ethanol concentration decreases with storage. The feasibility of measuring a forensically meaningful blood ethanol concentration in antemortem blood samples stored refrigerated (~4°C) from 4-7years after the blood draw was evaluated in this research. All blood samples were collected into two 10-ml gray top Vacutainer® tubes as part of police driving under the influence investigations. In 29 cases, blood in the tube originally analyzed was retested after 5-7years of refrigerated storage. Blood in 41 cases was analyzed in a previously unopened blood tube from the case after 4-7years of refrigerated storage. The first analysis of blood in each case occurred within 35days of the blood draw. Initial blood ethanol concentrations ranged from 0.094g/dl to 0.301g/dl. No samples showed an increase in ethanol concentration with storage that exceeded the uncertainty of the initial measurement. All decreases in ethanol concentration were less than 0.020g/dl. The mean differences in ethanol concentration in previously opened and unopened tubes were -0.014g/dl and -0.010g/dl, respectively. The results of this research support that antemortem blood in previously opened and unopened refrigerated blood tubes can be analyzed for ethanol content more than 4years and as much as 7years after the blood draw and provide a result consistent with the amount of ethanol loss expected from a test done within 1-3years of the blood draw.