Preanalytical Factors Influencing the Results of Ethanol Analysis in Postmortem Specimens.

Excessive drinking and drunkenness are underlying factors in many fatal accidents, which makes the quantitative determination of ethanol in postmortem (PM) specimens an essential part of all unnatural death investigations. The same analytical methods are used to determine ethanol in blood taken from living and deceased persons, although in medical examiner cases interpretation of the results is more complicated, owing to various pre-analytical factors. The biggest problem is that under anaerobic conditions ethanol can be produced naturally in decomposed bodies by microbial activity and fermentation of blood glucose. Ways are needed to differentiate antemortem (AM) ingestion of ethanol from PM synthesis. One approach involves determination of ethanol in alternative specimens, such as bile, cerebrospinal fluid (CSF), vitreous humor (VH) and/or urine, and comparison of results with blood-alcohol concentration (BAC). Another involves the analysis of various alcohol biomarkers, such as ethyl glucuronide (EtG), ethyl sulfate (EtS), and/or phosphatidylethanol (PEth) or the urinary metabolites of serotonin (5-HTOL/5-HIAA). If ethanol had been produced in the body by microbial activity, the blood samples should also contain other low-molecular volatiles, such as acetaldehyde, n-propanol, and/or n-butanol. The inclusion of 1-2% w/v sodium or potassium fluoride, as enzyme inhibitor, to all PM specimens is essential to diminish the risk of ethanol being generated after sampling, such as during shipment, and storage prior to analysis. Furthermore, much might be gained if the analytical cut-off for reporting positive BAC was raised from 0.01 g% to 0.02 g%, when PM blood are analyzed. Low BACs are more often produced after death than high BAC. Therefore, when the cadaver is obviously decomposed, a pragmatic approach would be to subtract 0.05 g% from the mean analytical result. Any remaining BAC is expected to give a more reliable indication of whether alcohol had been consumed before death.