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Endocrinology and Metabolism |
1 Garvan Institute of Medical Research and Department of Endocrinology, Sydney, Australia;2 Australian Sports Drug Testing Laboratory, National Measurement Institute, Sydney, Australia;3 ANZAC Research Institute, Concord Hospital, University of Sydney, Sydney, Australia;4 Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, Sydney, Australia.
aAddress correspondence to this author at: Pituitary Research Unit, Garvan Institute of Medical Research, 384 Victoria St, Darlinghurst 2010 Australia. Fax 0612 9295 8481; e-mail K.Ho{at}garvan.org.au.
Background: The utility of insulinlike growth factor (IGF) axis and collagen markers for a growth hormone (GH) doping test in sport depends on their stability and reproducibility. We sought to determine short-term within-subject variability of these markers in a large cohort of healthy individuals.
Methods: We measured IGF-I, IGF binding protein 3 (IGFBP-3), acid labile subunit (ALS), and the collagen markers N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (ICTP), and N-terminal propeptide of type III procollagen (PIIINP) in serum samples obtained on multiple occasions (median 3 per participant) over a 2- to 3-week period from 1103 elite athletes (699 men, 404 women) ages 22.2 (5.2) years [mean (SD)]. We estimated between-subject and within-subject variances by mixed–effects ANOVA.
Results: Within-subject variance accounted for 32% to 36% and 4% to 13% of the total variance in IGF markers and collagen markers, respectively. The within-subject CV ranged from 11% to 21% for the IGF axis markers and from 13% to 15% for the collagen markers. The index of individuality for the IGF axis markers was 0.66–0.76, and for the collagen markers, 0.26–0.45. For each marker, individuals with initial extreme measured values tended to regress toward the population mean in subsequent repeated measurements. We developed a Bayesian model to estimate the long-term probable value for each marker.
Conclusions: These results indicate that in healthy individuals the within-subject variability was greater for IGF-I than for the collagen markers, and that where a single measurement is available, it is possible to estimate the long-term probable value of each of the markers by applying the Bayesian approach. Such an application can increase the reliability and decrease the cost of detecting GH doping.
The following articles in journals at HighWire Press have cited this article:
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  S. Bhasin, E. J. He, M. Kawakubo, E. T. Schroeder, K. Yarasheski, G. J. Opiteck, A. Reicin, F. Chen, R. Lam, J. A. Tsou, et al. N-Terminal Propeptide of Type III Procollagen as a Biomarker of Anabolic Response to Recombinant Human GH and Testosterone J. Clin. Endocrinol. Metab., November 1, 2009; 94(11): 4224 - 4233. [Abstract] [Full Text] [PDF]
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S. T. Bennett There's Nothing to Winning, Really Clin. Chem., August 1, 2008; 54(8): 1265 - 1267. [Full Text] [PDF]
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