Combined statistical decision limits based on two GH-2000 scores for the detection of growth hormone misuse

Wei Liu, Frank Bretz, Dankmar Boehning, Richard IG Holt, Yang Han, Walailuck Boehning, Nishan Guha, David A. Cowan

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The GH-2000 biomarker method, based on the measurements of insulin-like growth factor-I (IGF-I) and the amino-terminal pro-peptide of type III collagen (P-III-NP), has been developed as a powerful technique for the detection of growth hormone (GH) misuse by athletes. IGF-I and P-III-NP are combined in gender specific formulas to create the GH-2000 score, which is used to determine whether GH has been administered. To comply with World Anti-Doping Agency regulations, each analyte must be measured by two methods. IGF-I and P-III-NP can be measured by a number of approved methods, each leading to its own GH-2000 score. Single decision limits for each GH-2000 score have been introduced and developed by Bassett, Erotokritou-Mulligan, Holt, Boehning and their co-authors in a series of papers. These have been incorporated into the guidelines of the World Anti-Doping Agency. A joint decision limit was constructed based on the sample correlation between the two GH-2000 scores generated from an available sample in order to increase the sensitivity of the biomarker method. This paper takes this idea further into a fully developed statistical approach. It constructs combined decision limits when two GH-2000 scores from different assay combinations are used to decide whether an athlete has been misusing GH. The combined decision limits are directly related to tolerance regions and constructed using a Bayesian approach. It is also shown to have highly satisfactory frequentist properties. The new approach meets the
required false-positive rate with a pre-specified level of certainty.
Original languageEnglish
JournalStatistical Methods in Medical Research
Publication statusAccepted/In press - 17 Mar 2022


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