The development of decision limits for the GH‐2000 detection methodology using additional insulin‐like growth factor‐I and amino‐terminal pro‐peptide of type III collagen assays

Abstract

The GH-2000 and GH-2004 projects have developed a method for detecting GH misuse based on measuring insulin-like growth factor-I (IGF-I) and the amino-terminal pro-peptide of type III collagen (P-III-NP). The objectives were to analyze more samples from elite athletes to improve the reliability of the decision limit estimates, to evaluate whether the existing decision limits needed revision, and to validate further non-radioisotopic assays for these markers. The study included 998 male and 931 female elite athletes. Blood samples were collected according to World Anti-Doping Agency (WADA) guidelines at various sporting events including the 2011 International Association of Athletics Federations (IAAF) World Athletics Championships in Daegu, South Korea. IGF-I was measured by the Immunotech A15729 IGF-I IRMA, the Immunodiagnostic Systems iSYS IGF-I assay and a recently developed mass spectrometry (LC-MS/MS) method. P-III-NP was measured by the Cisbio RIA-gnost P-III-P, Orion UniQ™ PIIINP RIA and Siemens ADVIA Centaur P-III-NP assays. The GH-2000 score decision limits were developed using existing statistical techniques. Decision limits were determined using a specificity of 99.99% and an allowance for uncertainty because of the finite sample size. The revised Immunotech IGF-I - Orion P-III-NP assay combination decision limit did not change significantly following the addition of the new samples. The new decision limits are applied to currently available non-radioisotopic assays to measure IGF-I and P-III-NP in elite athletes, which should allow wider flexibility to implement the GH-2000 marker test for GH misuse while providing some resilience against manufacturer withdrawal or change of assays.

A correction to the age-adjustment of the GH-2000 score used in the detection of growth hormone misuse

“…The development of the GH-2000 score has been reported previously in [6, 7]. It has the theoretical or model formwhere the coefficients have different values for male and female athletes.…”

“…The GH-2000 score was initially developed using immunoassays that are no longer available [4, 5]. Although the original discriminant function has remained unchanged, the decision limits have been updated as further experience has been accumulated and new assays have become available [6]. …”

“…For more details and background on these assays see [6]. As these assays do not give identical results, different GH-2000 scores are obtained with each of the combinations and as a result the decision limits are different, depending on the assay pair used.…”

Detection of Growth Hormone Releasing Peptides in Serum by a Competitive Receptor Binding Assay

“…The serum is a valuable matrix used for analysis of some doping substances e.g., CERA [30], human chorionic gonadotrophin [31], and growth hormone [32,33]. A GHRPs screening method for anti-doping control in serum samples would be highly desirable.…”

Methods for Doping Detection

“…Some issues persisted regarding plasma volume variation related to hydration, but the range of such changes was small compared to the DL and mean Score [9] . After inclusion of more results, the final DLs were published, and the test was implemented in anti-doping laboratories [10] .…”