Comparison among plasma, serum, and whole blood ethanol concentrations: impact of storage conditions and collection tubes.

How blood samples are processed and stored before being analyzed for alcohol levels is of concern in the forensic and toxicological fields, and is important in the standardization of research methods. This experiment explored for systematic differences in ethanol levels among several methods of processing and storing blood samples. Five adults consumed a standard alcoholic drink (0.7 g/kg) over a 15-min period, and blood samples were taken 5 times during a 3-h period following drinking onset. Samples for plasma and whole blood were drawn into Vacutainers containing either an anticoagulant or an anticoagulant plus preservative. Samples for serum were drawn into Vacutainers containing no additives or a preservative only. Separate sets of samples were analyzed on the day of the study, after storage at room temperature (25 degrees C) for 24 h, after storage at room temperature for 10 days, or after 10 days of refrigerated storage. Neither processing condition (i.e., type of additive) nor storage condition significantly affected ethanol levels. Consistent with the literature, plasma and serum samples had significantly higher concentrations of ethanol than whole blood. This study shows that blood samples containing ethanol at levels ranging from 60 to 90 mg/dL (0.06 to 0.09 mg%) are not significantly altered by the type of collection tube used or storage condition during a 10-day period.