Total body water is the preferred method to use in forensic blood-alcohol calculations rather than ethanol's volume of distribution

Peter D Maskell; A Wayne Jones; Steven B Heymsfield; Sue Shapses; Atholl Johnston

doi:10.1016/j.forsciint.2020.110532

Total body water is the preferred method to use in forensic blood-alcohol calculations rather than ethanol's volume of distribution

Forensic Sci Int. 2020 Nov:316:110532. doi: 10.1016/j.forsciint.2020.110532. Epub 2020 Oct 2.

Authors

Peter D Maskell¹, A Wayne Jones², Steven B Heymsfield³, Sue Shapses⁴, Atholl Johnston⁵

Affiliations

¹ Forensic Medicine and Science, University of Glasgow, Glasgow, G12 8QQ, UK. Electronic address: peter.maskell@glasgow.ac.uk.
² Division of Drug Research, Department of Biomedical and Clinical Sciences, Linköping University, SE-581 85, Linköping, Sweden.
³ Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, LA, USA.
⁴ Department of Nutritional Sciences, Rutgers University, New Brunswick, NJ, USA.
⁵ Clinical Pharmacology, Queen Mary University of London, London, EC1M 6BQ, UK; Analytical Services International, St George's-University of London, London, SW17 0RE, UK.

PMID: 33099270
DOI: 10.1016/j.forsciint.2020.110532

Abstract

During the prosecution and defence of drink-driving cases, forensic practitioners are often required to engage in various blood-alcohol calculations, such as whether or not the statutory limit was exceeded (e.g. 80mg/100mL, 0.08g/100mL or 0.80g/L). For this purpose, most forensic scientists utilize the Widmark equation, or some modification thereof, to calculate a person's blood alcohol concentration (BAC) based on information about the amount of ethanol consumed and the pattern of drinking. This equation comes in two main forms; one of which incorporates the apparent volume of distribution of ethanol (V) and the other a person's total body water (TBW). In this study, we utilised two independent data sets, one involving the determination of V for ethanol in 173 men and 63 women, and the other TBW determined for 582 men and 884 women. Those subjects included in the TBW group represented various racial groups (Caucasians, African Americans, Hispanics, Asians and Puerto Ricans), with body mass index (BMI) ranging from 17 to 80kg/m². Both versions of the Widmark equation were evaluated in relation to their accuracy and precision in predicting TBW and/or V using the two most common anthropometric equations; those of Watson et al. and Forrest. Both anthropometric equations exhibited good accuracy (<4.3%) for the prediction of both TBW and V. However, the root mean square error was lower TBW was used for prediction (9.09-12.84%) rather than V (11.72-15.08%). Overall, this study has demonstrated (a) that blood-alcohol calculations are more reliable using TBW rather than V (b) that both equations (Watson et al. and Forrest) are applicable to ethnic groups other than Caucasians and (c) the Forrest equation predicts TBW in men and women with BMI from 17 to 35kg/m² and that the Watson et al. equation works for those with more extreme BMI; females (17-80kg/m²) and males (17-67kg/m²).

Keywords: Analysis; Blood-alcohol calculations; Body-water; Distribution volume; Ethanol; Forensic technical defences; Pharmacokinetics; Widmark equation.

MeSH terms

Blood Alcohol Content*
Body Mass Index
Body Water / metabolism*
Central Nervous System Depressants / pharmacokinetics
Datasets as Topic
Ethanol / pharmacokinetics
Female
Forensic Toxicology / methods*
Humans
Male
Mathematical Concepts*

Substances

Blood Alcohol Content
Central Nervous System Depressants
Ethanol