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Clin Chem. 2001 Feb;47(2):292-300.

Performance characteristics of a carbon isotope ratio method for detecting doping with testosterone based on urine diols: controls and athletes with elevated testosterone/epitestosterone ratios.

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UCLA Olympic Analytical Laboratory, Department of Molecular and Medical Pharmacology, University of California at Los Angeles, Los Angeles, CA 90025, USA.



Carbon isotope ratio methods are used in doping control to determine whether urinary steroids are endogenous or pharmaceutical.


Gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) was used to determine the delta(13)C values for 5 beta-androstane-3 alpha,17 beta-diyl diacetate (5 beta A), 5 alpha-androstane-3 alpha,17 beta-diyl diacetate (5 alpha A), and 5 beta-pregnane-3 alpha,20 alpha-diyl diacetate (5 beta P) in a control group of 73 healthy males and 6 athletes with testosterone/epitestosterone ratios (T/E) >6.


The within-assay precision SDs for 5 beta A, 5 alpha A, and 5 beta P were +/- 0.27 per thousand, +/- 0.38 per thousand, and +/- 0.28 per thousand, respectively. The between-assay precision SDs ranged from +/- 0.40 per thousand to +/- 0.52 per thousand. The system suitability and batch acceptance scheme is based on SDs. For the control group, the mean delta(13)C (SD) values were -25.69 per thousand (+/- 0.92 per thousand), -26.35 per thousand (+/- 0.68 per thousand), and -24.26 per thousand (+/- 0.70 per thousand), for 5 beta A, 5 alpha A, and 5 beta P, respectively. 5 beta P was greater than 5 beta A and 5 alpha A (P <0.01), and 5 beta A was greater than 5 alpha A (P <0.01). The means - 3 SD were -28.46 per thousand, -28.39 per thousand, and -26.37 per thousand for 5 beta A, 5 alpha A, and 5 beta P, respectively. The maximum difference between 5 beta P and 5 beta A was 3.2 per thousand, and the maximum 5 beta A/5 beta P was 1.13. Three athletes with chronically elevated T/Es had delta(13)C values consistent with testosterone administration and three did not.


This GC-C-IRMS assay of urine diols has low within- and between-assay SDs; therefore, analysis of one urine sample suffices for doping control. The means, SDs, +/-3 SDs, and ranges of delta(13)C values in a control group are established. In comparison, testosterone users have low 5 beta A and 5 alpha A, large differences between 5 beta A or 5 alpha A and 5 beta P, and high 5 beta A/5 beta P and 5 alpha A/5 beta P ratios.

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