Universität zu Köln

Flenker, Ulrich, Geppert, Leo N. and Ickstadt, Katja (2012). Validity of stable isotope data in doping control: perspectives and proposals. Drug Test. Anal., 4 (12). S. 934 - 942. HOBOKEN: WILEY. ISSN 1942-7611

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Abstract

?13C and d13C values of endogenous urinary steroids represent physiological random variables. Measurement uncertainty and biological scatter likewise contribute to the variances. The statistical distributions of negative controls are well investigated, but there is little knowledge about the corresponding distributions of steroid-users. For these reasons valid discrimination of steroid users from non-users by 13C/12C analysis of endogenous steroids requires elaborate statistical treatment. Corresponding Bayesian approaches are presented following an introduction to the rationale. The use of mixture models appears appropriate. The distribution of routine data has been deconvolved and characterized accordingly. The mixture components, which presumably represent steroid users and non-users, exhibit considerable overlap. The validity of a given result depends on both the analytical uncertainty and the prior probability of doping offenses. Low analytical uncertainties but high prior probabilities facilitate valid detection of doping offenses. Two recommendations can be deduced. First, before starting an 13C/12C analysis, any initial suspicion should be well-substantiated. This precludes use of permissive criteria derived from the steroid profile. Secondly, knowledge of relevant 13C/12C distributions is required. This must cover representative numbers of authentic steroid users. Finally, it is desirable that the conditional probability for steroid administration rather than the measurement uncertainty is calculated and reported. This quantity possesses superior validity and it is largely independent of laboratory bias. The findings suggest and facilitate flexible handling of decision limits. Proposals for the evaluation of stable isotope data are presented. Copyright (c) 2012 John Wiley & Sons, Ltd.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Flenker, Ulrich UNSPECIFIED UNSPECIFIED UNSPECIFIED Geppert, Leo N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Ickstadt, Katja UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-477283
DOI:	10.1002/dta.1398
Journal or Publication Title:	Drug Test. Anal.
Volume:	4
Number:	12
Page Range:	S. 934 - 942
Date:	2012
Publisher:	WILEY
Place of Publication:	HOBOKEN
ISSN:	1942-7611
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language Biochemical Research Methods; Chemistry, Analytical; Pharmacology & Pharmacy Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/47728