Long-Term Blood Alcohol Stability in Forensic Antemortem Whole Blood Samples

The effect of long-term room temperature storage on the stability of ethanol in whole blood specimens was investigated. One hundred and seventeen preserved whole blood case samples (110 of 117 with two tubes of blood in each case) were used for this study. One tube from each case was initially tested for blood alcohol concentration (BAC) for criminal driving under the influence proceedings. Cases positive for ethanol ranged in BAC from 0.023 to 0.281 g/dL. The second tube, if present, remained sealed. All blood samples were then stored at room temperature. After 5.4-10.3 years, the opened tubes were reanalyzed for BAC by the same laboratory that performed the initial testing using the same method and same instrumentation. After the same storage period, the unopened tubes were sent to a different laboratory, using a different method and different instrumentation, and reanalyzed for BAC after a total of 5.6-10.5 years of room temperature storage. Seven samples initially negative for alcohol remained negative. All samples initially positive for ethanol demonstrated a decrease in BAC over time with a statistically significant difference in loss observed based on blood sample volume and whether or not the tube had been previously opened. The decrease in BAC ranged from 0.005 to 0.234 g/dL. Tubes that were not previously opened and were more than half full demonstrated better BAC stability with 89% of these tubes demonstrating a loss of BAC between 0.01 and 0.05 g/dL.