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Variability of blood alcohol content (BAC) determinations: The role of measurement uncertainty, significant figures, and decision rules for compliance assessment in the frame of a multiple BAC threshold law
Author(s) -
Zamengo Luca,
Frison Giampietro,
Tedeschi Gianpaola,
Frasson Samuela,
Zancanaro Flavio,
Sciarrone Rocco
Publication year - 2014
Publication title -
drug testing and analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.065
H-Index - 54
eISSN - 1942-7611
pISSN - 1942-7603
DOI - 10.1002/dta.1614
Subject(s) - rounding , blood alcohol content , computer science , blood alcohol , set (abstract data type) , statistics , operations research , poison control , mathematics , medicine , injury prevention , environmental health , programming language , operating system
The measurement of blood‐alcohol content (BAC) is a crucial analytical determination required to assess if an offence (e.g. driving under the influence of alcohol) has been committed. For various reasons, results of forensic alcohol analysis are often challenged by the defence. As a consequence, measurement uncertainty becomes a critical topic when assessing compliance with specification limits for forensic purposes. The aims of this study were: (1) to investigate major sources of variability for BAC determinations; (2) to estimate measurement uncertainty for routine BAC determinations; (3) to discuss the role of measurement uncertainty in compliance assessment; (4) to set decision rules for a multiple BAC threshold law, as provided in the Italian Highway Code; (5) to address the topic of the zero‐alcohol limit from the forensic toxicology point of view; and (6) to discuss the role of significant figures and rounding errors on measurement uncertainty and compliance assessment. Measurement variability was investigated by the analysis of data collected from real cases and internal quality control. The contribution of both pre‐analytical and analytical processes to measurement variability was considered. The resulting expanded measurement uncertainty was 8.0%. Decision rules for the multiple BAC threshold Italian law were set by adopting a guard‐banding approach. 0.1 g/L was chosen as cut‐off level to assess compliance with the zero‐alcohol limit. The role of significant figures and rounding errors in compliance assessment was discussed by providing examples which stressed the importance of these topics for forensic purposes. Copyright © 2014 John Wiley & Sons, Ltd.