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Fermentation in Blood Samples Produce....Alcohol

Fermentation in Blood Samples Produce....Alcohol

Information courtesy of Lawrence Taylor - DUIblog

In a post a couple of days ago, I discussed the necessity of adding an anticoagulant to blood samples taken in DUI cases to avoid an elevated blood alcohol result due to clotting. I also mentioned in that post that if a preservative were not also added to the sample, fermentation can take place. That prompted a number of queries about fermentation in blood alcohol analysis....

Blood is an organic substance and, like any organic substance, will decompose because of enzymes and bacterial action. One of the results of decomposition is that alcohol is created in the blood. In a blood sample originally containing no alcohol, decomposition and resulting fermentation can cause a reading far above the legal limit, depending upon the stage of decay.

To stop or at least slow down this process, a preservative (usually sodium fluoride) is added to the sample, and it should also be refrigerated until analyzed by the crime lab. The amount of preservative, of course, must be sufficient, and it must be actively mixed into the blood sample. While it is common among law enforcement agencies to use 20mg of sodium fluoride, many experts view this as insufficient. See, for example, Dick and Stone, "Alcohol Loss Arising from Microbial Contamination of Drivers' Blood Specimens", 34 Forensic Science International 17 (1987). Further, although labs often take a week or more before receiving and analyzing blood samples, normal levels of sodium fluoride will render the sample stable for only about two days. Kaye, "The Collection and Handling of the Blood Alcohol Specimen", 74 American Journal of Clinical Pathology 743 (1980).

To complicate things further, not all microorganisms are affected by sodium fluoride. As researchers have discovered, one such microbe that is commonly found in the human body is Candida albicans:

It has been shown that several microorganisms occasionally found in blood specimens are capable of producing ethyl alcohol. Although (one study) found that sodium fluoride effectively inhibited alcohol production from a variety of microorganisms, one -- Candida

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