Observations on interpretation of blood alcohol levels derived from analysis of urine.

Abstract

For many years it has been customary to derive blood alcohol concentrations from the analysis of urine, and despite the fact that the accuracy of such derivations has often been questioned British courts have been content to accept them as evidence in prosecutions for drunken driving, presumably on the grounds that such evidence was merely confirmatory and not vital. However, with the impending change in the law which will make it an offence to drive with more than a stated amount of alcohol in the blood, the reliability of the method of determining blood alcohol concentrations assumes much greater significance, particularly as the use of urine analysis has not been excluded (Ministry of Transport, 1965).In the interpretation of blood levels derived from urine analysis two problems arise. The first concerns the accuracy of the analytical method used to measure the alcohol concentration in urine, and the second is related to the choice of the conversion factor for the derivation of blood level. In the case of urine analysis the accuracy of the Nickolls modification of the Cavett technique is well established, but the method is tedious, time-consuming, and critically dependent on the technical skill of the operator. Gas chromatography is free from these disadvantages (Chandela and Janaik, 1960), and it is claimed that when used in combination with an internal standard and an integrator the alcohol content of a minute sample of either blood or urine can be measured accurately within five minutes (Curry, Walker, and Simpson, 1966). One purpose of the investigation to be described was to determine the accuracy of the gas chromatographic method.In the case of the conversion factor no unanimity of opinion exists about the correct choice, and it was the second purpose of the investigation to examine the validity of the conversion factor of 1.33 recommended in the Report of a Special Committee of the British Medical Association (1965 The times at which the samples were obtained were noted and the samples themselves were divided into three equal parts for distribution to the suspect, the police laboratory, and this department. Anonymity was preserved by the designation of a reference number. Initially the samples were analysed both by the Nickolls (1960) modification of the Cavett technique and by the gas chromatographic technique described in detail by Curry et al. (1966) but modified to use a Poropak Q porous polymer bead column instead of a polyethylene glycol 400 column. The Poropak column offers the advantage of a much lower column bleed and elutes the water peak first after 30 seconds followed by ethanol at 1.5 minutes and n-propanol at 3.5 minutes. With polyethylene glycol, unless the column is carefully conditioned with water before use, a tailing water peak is produced which prolongs the analysis. Latterly the samples were analysed by the gas chromatographic method alone.For chromatographic analysis the blood or urine sample was diluted with ten times its volume of an aqueous solution containing 24 mg. of propra...

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Effect of Chronic Ethanol Feeding on Hepatic Collagen in the Monkey

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