Evaluation of immunoassays for the measurement of insulin-like growth factor-I and procollagen type III peptide, indirect biomarkers of recombinant human growth hormone misuse in sport

Noble metal nanostructures in optical biosensors: Basics, and their introduction to anti-doping detection

Nanotechnology has illustrated significant potentials in biomolecular-sensing applications; particularly its introduction to anti-doping detection is of great importance. Illicit recreational drugs, substances that can be potentially abused, and drugs with dosage limitations according to the prohibited lists announced by the World Antidoping Agency (WADA) are becoming of increasing interest to forensic chemists. In this review, the theoretical principles of optical biosensors based on noble metal nanoparticles, and the transduction mechanism of commonly-applied plasmonic biosensors are covered. We review different classes of recently-developed plasmonic biosensors for analytic determination and quantification of illicit drugs in anti-doping applications. The important classes of illicit drugs include anabolic steroids, opioids, stimulants, and peptide hormones. The main emphasis is on the advantages that noble metal nano-particles bring to optical biosensors for signal enhancement and the development of highly sensitive (label-free) biosensors. In the near future, such optical biosensors may be an invaluable substitute for conventional anti-doping detection methods such as chromatography-based approaches, and may even be commercialized for routine anti-doping tests.

Growth hormone doping in sports: a critical review of use and detection strategies

GH is believed to be widely employed in sports as a performance-enhancing substance. Its use in athletic competition is banned by the World Anti-Doping Agency, and athletes are required to submit to testing for GH exposure. Detection of GH doping is challenging for several reasons including identity/similarity of exogenous to endogenous GH, short half-life, complex and fluctuating secretory dynamics of GH, and a very low urinary excretion rate. The detection test currently in use (GH isoform test) exploits the difference between recombinant GH (pure 22K-GH) and the heterogeneous nature of endogenous GH (several isoforms). Its main limitation is the short window of opportunity for detection (~12-24 h after the last GH dose). A second test to be implemented soon (the biomarker test) is based on stimulation of IGF-I and collagen III synthesis by GH. It has a longer window of opportunity (1-2 wk) but is less specific and presents a variety of technical challenges. GH doping in a larger sense also includes doping with GH secretagogues and IGF-I and its analogs. The scientific evidence for the ergogenicity of GH is weak, a fact that is not widely appreciated in athletic circles or by the general public. Also insufficiently appreciated is the risk of serious health consequences associated with high-dose, prolonged GH use. This review discusses the GH biology relevant to GH doping; the virtues and limitations of detection tests in blood, urine, and saliva; secretagogue efficacy; IGF-I doping; and information about the effectiveness of GH as a performance-enhancing agent.

Serum insulin-like growth factor-I and pro-collagen type III N-terminal peptide in adolescent elite athletes: implications for the detection of growth hormone abuse in sport

CONTEXT

A method based on two GH-dependent markers, IGF-I and pro-collagen type III N-terminal peptide (P-III-P), has been devised to detect exogenously administered GH. Because previous studies on the detection of GH abuse involved predominantly adult athletes, the method must be validated in adolescent athletes.

OBJECTIVE

The aim of the study was to examine serum IGF-I and P-III-P concentrations in elite adolescent athletes and to determine whether the method developed in adults is appropriate to detect GH abuse in this population.

DESIGN AND SETTING

We conducted a cross-sectional observational study at national sporting organization training events.

SUBJECTS

A total of 157 (85 males, 72 females) elite athletes between 12 and 20 yr of age participated in the study.

INTERVENTION

Serum IGF-I and P-III-P were each measured by two commercially available immunoassays. GH-2000 discriminant function scores were calculated.

RESULTS

Both IGF-I and P-III-P rose to a peak during adolescence, which was earlier in girls than in boys. All GH-2000 scores lay below the proposed cutoff limit of 3.7 (although some scores were close to this value), indicating that none of these athletes would be accused of GH doping if the GH-2000 discriminant formulae were used. The results between the two immunoassays for IGF-I and P-III-P were closely aligned.

CONCLUSIONS

The GH-2000 score rises in early adolescence, reaches a peak in athletes aged 13-16 yr, and then falls. We have found no evidence that the proposed GH-2000 score developed in adults would lead to an unacceptable rate of false-positive results in adolescent athletes, but caution may be required around the time of peak growth velocity.

Surface plasmon resonance immuno assays - A perspective

Human growth hormone (GH) represents an extremely challenging task from an anti-doping viewpoint. GH is an endogenously produced substance, present at very low levels in circulation (for the most abundant 22kDa isoform approximately 50pM in plasma and 100fM in urine) either as monomer or homo- and heterodimers, comprises a family of distinct isoforms, and obeys a pulsatile secretion routine that is affected by many different internal and external factors. Upon administration of the recombinant, single-isoform pharmaceutical, the feedback mechanism reduces the endogenous heterogeneity resulting in altered ratios between the different GH isoforms. Thus, measuring the isoform ratios through immuno assays appears the approach of choice. Conventional assays do not provide information on isoform-specific association and dissociation events of the individual primary antibody-isoform or isoform-secondary antibody interactions. This particular information can be obtained using the technology of surface plasmon resonance (SPR) which enables monitoring of biomolecular interactions in a dynamic and label-free setting. In this paper the different aspects of SPR are described, how the technology may be beneficial for understanding today's anti-GH immunoassays, and whether the approach could be employed for measuring GH in the near future.

Moving one step closer to catching the GH cheats: The GH-2004 experience

Growth hormone is abused by athletes for its anabolic and lipolytic properties. The detection of GH abuse is challenging because it is an endogenous hormone whose concentration varies widely in any one day. The GH-2000 project proposed a test based on the measurement of IGF-I and type III pro-collagen (P-III-P). When the results of the GH-2000 project were presented to an expert workshop, the method was supported but it was felt that several issues needed to be resolved before the method could be adopted. The first was a potential effect of ethnicity as most subjects in the GH-2000 were white Europeans and the second was a possible effect of injury as P-III-P is a marker of soft tissue turnover. The GH-2004 project was conceived to address these concerns. The GH-2004 project has shown that while there are minor differences in IGF-I and P-III-P between ethnicities, these are small and do not affect the performance of the test. Injury leads to a small rise in P-III-P but again this is not of sufficient magnitude to affect the performance of the test. The GH-2004 project has provided further support for the marker approach as a means of detecting GH abuse in athletes. As WADA have not developed their own immunoassays, however, further work is needed to validate newer commercial assays measuring IGF-I and P-III-P to establish reliable conversion factors to the original GH-2000 units to allow the published formulae to be used.

Statistical issues in implementing the marker method

The detection of growth hormone (GH) abuse by athletes raises statistical problems as well as biochemical ones. We outline the statistical approaches to the various issues which have arisen during the work of the GH-2000 and GH-2004 teams; in particular, it considers the need to develop a test which detects GH abuse in any elite athlete 'beyond reasonable doubt'. The test needs to be robust enough to withstand legal challenge, while minimising the risk of false accusation. The paper identifies various issues which arise in the development of such a test, and describes how these were resolved. Since GH is a naturally occurring hormone whose concentration varies substantially, its abuse cannot be detected by direct measurement. The methodology considered here made use of markers whose levels are more stable but are influenced by GH. The statistical methods employed aimed to make the best use of these markers, taking account of all factors contributing to errors in measurement. There were two key steps in the statistical investigation undertaken to develop the GH detection algorithm. The first was the requirement to identify GH-dependent biomarkers which would identify GH doping reliably and robustly for a significant length of time. The second was to calibrate the GH detection method in the elite athlete population, so that the method would be applicable to all athletes, regardless of age, sex and ethnicity, and regardless of whether they had recently sustained an injury. In practice, further work was needed to ensure that the methodology met the WADA testing protocol rules, but also that the proposed method can be used by any WADA accredited lab without placing any athlete at an unfair disadvantage and ensuring a high level of confidence in any result produced.

Laboratory issues in the implementation of the marker method

Two important biomarkers for the identification of growth hormone or IGF-I administration are IGF-I and P-III-P. These substances are determined in plasma or preferably in serum. There are a number of assays on the market for IGF-I but only two for P-III-P. The principles behind these assays and the choice of assays for doping control purposes are discussed. The future possibility of quantification by mass spectrometry is also briefly discussed.

The analytical chemistry of drug monitoring in athletes

The detection and deterrence of the abuse of performance-enhancing drugs in sport are important to maintaining a level playing field among athletes and to decreasing the risk to athletes' health. The World Anti-Doping Program consists of six documents, three of which play a role in analytical development: The World Anti-Doping Code, The List of Prohibited Substances and Methods, and The International Standard for Laboratories. Among the classes of prohibited substances, three have given rise to the most recent analytical developments in the field: anabolic agents; peptide and protein hormones; and methods to increase oxygen delivery to the tissues, including recombinant erythropoietin. Methods for anabolic agents, including designer steroids, have been enhanced through the use of liquid chromatography/tandem mass spectrometry and gas chromatography/combustion/isotope-ratio mass spectrometry. Protein and peptide identification and quantification have benefited from advances in liquid chromatography/tandem mass spectrometry. Incorporation of techniques such as flow cytometry and isoelectric focusing have supported the detection of blood doping.

Influence of ethnicity on IGF-I and procollagen III peptide (P-III-P) in elite athletes and its effect on the ability to detect GH abuse

CONTEXT

A method based on the two GH dependent markers, IGF-I and procollagen III peptide (P-III-P) has been proposed to detect exogenously administered GH. As previous studies involved predominantly white European elite athletes, it is necessary to validate the method in other ethnic groups.

OBJECTIVE

To examine serum IGF-I and P-III-P in elite athletes of different ethnicities within 2 h of competing at national or international events.

DESIGN

Cross-sectional observational study.

SETTING

National and International sporting events.

SUBJECTS

1085 elite athletes of different ethnicities.

INTERVENTION

Serum IGF-I and P-III-P were measured and GH-2000 discriminant function score was calculated. Effect of ethnicity was assessed.

RESULTS

In men, IGF-I was 21.7 +/- 2.6% lower in Afro-Caribbeans than white Europeans (P < 0.0001) but there were no differences between other ethnic groups. In women, IGF-I was 14.2 +/- 5.1% lower in Afro-Caribbeans (P = 0.005) and 15.6 +/- 7.0% higher in Orientals (P = 0.02) compared with white Europeans. P-III-P was 15.2 +/- 3.5%, 26.6 +/- 6.6% and 19.3 +/- 5.8% lower in Afro-Caribbean (P < 0.0001), Indo-Asian (P < 0.0001) and Oriental men (P = 0.001), respectively, compared with white European men. In women, P-III-P was 15.7 +/- 4.7% lower in Afro-Caribbeans compared to white Europeans (P =0.0009) but there were no differences between other ethnicities. Despite these differences, most observations were below the upper 99% prediction limits derived from white European athletes. All GH-2000 scores lay below the cut-off limit proposed for doping.

CONCLUSIONS

The GH-2000 detection method based on IGF-I and P-III-P would be valid in all ethnic groups.

Idiopathic short stature: definition, epidemiology, and diagnostic evaluation

Idiopathic short stature is a condition in which the height of the individual is more than 2 SD below the corresponding mean height for a given age, sex and population, in whom no identifiable disorder is present. It can be subcategorized into familial and non-familial ISS, and according to pubertal delay. It should be differentiated from dysmorphic syndromes, skeletal dysplasias, short stature secondary to a small birth size (small for gestational age, SGA), and systemic and endocrine diseases. ISS is the diagnostic group that remains after excluding known conditions in short children.

Validation of the growth hormone (GH)-dependent marker method of detecting GH abuse in sport through the use of independent data sets

CONTEXT

The detection of exogenously administered growth hormone (GH) poses a formidable challenge but a detection method based on the measurement of two GH-dependent markers, IGF-I and type 3 pro-collagen (P-III-P) has been proposed. The measurement of multiple markers in conjunction with discriminant functions can improve the sensitivity and specificity of detection compared with single marker analysis.

OBJECTIVE

To provide further validation of the GH-dependent marker approach.

DESIGN

Analysis of discriminant function scores for GH detection on independent datasets.

SETTING

Two independent (GH-2000 and Kreischa) double blind, placebo controlled, hGH administration studies.

SUBJECTS

Healthy active male volunteers.

INTERVENTION

GH-2000 proposed a discriminant function involving IGF-I and P-III- P while the Kreischa function involved IGF-I, P-III-P and IGFBP-3. After adjustment for assay differences the formulae were applied to the other dataset.

OUTCOME MEASURES

Ability to detect GH use in independent datasets using a predefined specificity of approximately 1 in 10000.

RESULTS

The GH-2000 formula was able to detect 90% of those receiving GH in the Kreischa study at one or more time points during the study period. This sensitivity was similar to that obtained on the original GH-2000 dataset. The Kreischa formula correctly identified 41% of individuals receiving GH in the GH-2000 study.

CONCLUSIONS

The study provides further validation that the test proposed by GH-2000 based on IGF-I and P-III-P concentrations can be used to detect subjects receiving exogenous GH.

Enzyme-linked immunosorbent assays for insulin-like growth factor-I using six-histidine tag fused proteins

The fusion proteins of insulin-like growth factor-I (IGF-I) and six-histidine tag (IGF-I-6H, 6H-IGF-I-6H) were cloned, expressed, purified and renatured, with their immunoreaction properties and biological activities intact. The binding kinetics between these fusion proteins and anti-IGF-I antibody or anti-6H antibody were studied using surface plasmon resonance (SPR). Two enzyme-linked immunosorbent assay (ELISA) modes, which proved feasible in the measurement of human serum samples, were used to detect IGF-I with the help of the six-histidine tagged proteins. Furthermore, combining the production technique of the six-histidine tagged fusion protein with the competitive sandwich ELISA mode, using an enzyme labeled anti-6H antibody as a tracer, can be a universal immunochemical method to quantitate other polypeptides or proteins.

Expression and characterization of insulin growth factor-I-enhanced green fluorescent protein fused protein as a tracer for immunoassay

The insulin-like growth factor-I (IGF-I) is an important polypeptide hormone under investigation for body metabolism study and for doping detection. Here, we describe for the first time the expression of a recombinant fusion protein of IGF-I and the enhanced green fluorescent protein (EGFP). The genetic fusion approach enables preparation of conjugates with 1:1 stoichiometry and homogeneous structure. The fused protein (EGFP-IGF-I) was expressed as a soluble protein in cytoplasm of Escherichia coli and its fluorescence and immunoreaction properties were thoroughly characterized. Finally, we demonstrated the utility of the EGFP-IGF-I fusion protein for the fluorescence immunoassay of IGF-1. The linear range of the assay is 1.6 x 10(-8) to 2.0 x 10(-6) M with a detection limit of 1.6 x 10(-8) M. To our knowledge, this is the first time that EGFP has been used as a quantitative label in a fusion protein to develop a quantitative assay for IGF-I. Furthermore, the use of genetically engineered fusion proteins, which combine peptide hormones with fluorescent protein, can lead to a new labeling approach to a number of bioanalytical applications.

Challenges in Detecting the Abuse of Growth Hormone in Sport

Background: Growth hormone (GH) is reputed to be in widespread use in the sporting arena as a performance-enhancing agent and is on the list of banned substances published by the World Anti-Doping Agency. The detection of GH abuse poses many challenges. Unlike many substances of abuse, such as synthetic anabolic steroids, GH is a naturally occurring substance; therefore, demonstration of exogenous administration must rely on detecting concentrations in excess of an established reference interval. The purpose of this review is to discuss the methodologies being developed to detect GH abuse.

Methods: We undertook a comprehensive search using multiple electronic databases and hand searches of reference lists of articles. The data for this review reflect our academic interests and experience through work on the GH-2000 and GH-2004 projects.

Results: Two approaches have been taken to detect GH abuse. The first is based on assessment of the effect of exogenous GH on pituitary GH isoforms, and the second is based on measurement of markers of GH action. The advantages of each approach and the difficulties encountered with each technique, as well as future concepts in detection, are discussed.

Conclusion: Although there are substantial challenges for the detection of GH, methodologies now exist to detect GH abuse with reasonable sensitivity and specificity.