Laboratory screening for erythropoietin abuse in sport: an emerging challenge

Laboratory hematology in the history of Clinical Chemistry and Laboratory Medicine

Background: For the occasion of the 50th anniversary of the journal Clinical Chemistry and Laboratory Medicine (CCLM), an historic overview of papers that the journal has published in the field of laboratory hematology (LH) is presented.

Methods: All past volumes of CCLM were screened for papers on LH and these were categorized. Bibliographic data of these papers were also analyzed.

Results: CCLM published in total 387 LH papers. The absolute number of LH papers published annually showed a significant increase over the years since 1985. Also the share of LH papers demonstrated a steady increase (overall mean 5%, but mean 8% over the past 4 years). The most frequent category was coagulation and fibrinolysis (23.5%). Authors from Germany contributed the most LH papers to the journal (22.7%), followed by the Netherlands and Italy (16.3 and 13.2%, respectively). Recent citation data indicated that other publications cited LH review papers much more frequently than other types of papers.

Conclusions: The history of the journal reflects the emergence and development of laboratory hematology as a separate discipline of laboratory medicine.

Erythropoietin and other blood-boosting methods

Dating back to the earliest Olympics, athletes have been searching for a performance edge. Recombinant human erythropoietin was made commercially available in 1987 to treat various diseases associated with anemia. Within a few years, elite endurance athletes capitalized on its potential as an undetectable performance-enhancing agent. Although antidoping agencies have developed a test to detect its use, there are pitfalls. More importantly, athletes continue to add more sophisticated doping practices to their armamentarium, challenging regulatory agencies, putting their health at great risk, and tainting the spirit of fair competition.

LC−MS/MS Method for Confirmation of Recombinant Human Erythropoietin and Darbepoetin α in Equine Plasma

Recombinant human erythropoietin (rhEPO) and darbepoetin alpha (DPO) are protein-based drugs for the treatment of anemia by stimulating red blood cell production. Consequently, they are abused in human and equine sports. To deter their abuse in the horse racing industry, a sensitive and reliable method for confirmation of these agents in equine plasma has been in urgent need. Such a method by LC-MS/MS is described in this paper. The method involved analyte enrichment by immunoaffinity separation using anti-rhEPO antibody linked to magnetic beads, digestion by trypsin, and analysis by LC-MS/MS. Two specific proteotypic peptides, 46VNFYAWK52 and 144VYSNFLR150 from rhEPO and DPO were employed for confirmation of the analytes based on chromatographic retention times and major product ions. The limit of confirmation of this method was 0.2 ng/mL, and the limit of detection was 0.1 ng/mL for rhEPO and DPO in equine plasma. This method was successful in confirming the presence of rhEPO and DPO in plasma samples collected from research horses to which rhEPO or DPO was administered and from racehorses following competition and in noncompetition samples in North America. To our knowledge, this is the first LC-MS method with adequate sensitivity and specificity in providing unequivocal confirmation of rhEPO and DPO in equine plasma samples. This method provides a powerful enforcement tool that was lacking in the fight against the abuse of rhEPO and DPO in the horse racing industry.

Procedures for monitoring recombinant erythropoietin and analogues in doping control

The present report summarizes the main analytical strategies developed to identify the presence of recombinant erythropoietin (EPO) administered as a doping agent. Indirect evidence is based on the analysis of blood parameters (haemoglobin, haematocrit, reticulocytes, macrocytes, etc.) and serum markers (concentration of EPO and serum transferrin receptors, etc.). The problem of intertechnique comparison for reliable results evaluation is emphasized, especially for serum markers. Charge differences between isoforms of recombinant EPO and native urinary EPO are the grounds for the isoelectric focusing-double blotting-chemiluminescence detection method presently approved for doping control. Works addressing its advantages and limitations are presented and commented on. The chemical bases of the differential detection are highlighted and some future approaches for detection are also presented. The appearance and detectability of EPO analogues and mimetics susceptible for abuse are also addressed.

Biochemistry, physiology, and complications of blood doping: facts and speculation

Competition is a natural part of human nature. Techniques and substances employed to enhance athletic performance and to achieve unfair success in sport have a long history, and there has been little knowledge or acceptance of potential harmful effects. Among doping practices, blood doping has become an integral part of endurance sport disciplines over the past decade. The definition of blood doping includes methods or substances administered for non-medical reasons to healthy athletes for improving aerobic performance. It includes all means aimed at producing an increased or more efficient mechanism of oxygen transport and delivery to peripheral tissues and muscles. The aim of this review is to discuss the biochemistry, physiology, and complications of blood doping and to provide an update on current antidoping policies.

Blood doping by cobalt. Should we measure cobalt in athletes?

Background

Blood doping is commonplace in competitive athletes who seek to enhance their aerobic performances through illicit techniques.

Presentation of the hypothesis

Cobalt, a naturally-occurring element with properties similar to those of iron and nickel, induces a marked and stable polycythemic response through a more efficient transcription of the erythropoietin gene.

Testing the hypothesis

Although little information is available so far on cobalt metabolism, reference value ranges or supplementation in athletes, there is emerging evidence that cobalt is used as a supplement and increased serum concentrations are occasionally observed in athletes. Therefore, given the athlete's connatural inclination to experiment with innovative, unfair and potentially unhealthy doping techniques, cobalt administration might soon become the most suited complement or surrogate for erythropoiesis-stimulating substances. Nevertheless, cobalt administration is not free from unsafe consequences, which involve toxic effects on heart, liver, kidney, thyroid and cancer promotion.

Implications of the hypothesis

Cobalt is easily purchasable, inexpensive and not currently comprehended within the World Anti-Doping Agency prohibited list. Moreover, available techniques for measuring whole blood, serum, plasma or urinary cobalt involve analytic approaches which are currently not practical for antidoping laboratories. Thus more research on cobalt metabolism in athletes is compelling, along with implementation of effective strategies to unmask this potentially deleterious doping practice

Comparison of serum creatinine, uric acid, albumin and glucose in male professional endurance athletes compared with healthy controls

Owing to considerable physical, endocrinological and metabolic adaptations, the analysis of biochemical data in elite and top-class athletes requires caution. With the aim to identify metabolic and biochemical adaptations to particular lifestyle conditions, such as regular and strenuous physical exercise, we measured the concentration of serum albumin, creatinine, uric acid and glucose in 80 male professional cyclists, 37 male members of the Italian national cross-country ski team and 60 male healthy sedentary controls at rest. At variance with earlier investigations, endurance athletes showed significantly decreased concentrations of serum creatinine (controls: 83.1±11.0 μmol/l; skiers: 78.0±8.4 μmol/l; p<0.05; cyclists: 73.8±10.4 μmol/l; p<0.01), uric acid (controls: 362±69 μmol/l; skiers: 331±70 μmol/l; p<0.05; cyclists: 312±61 μmol/l; p<0.01) and glucose (controls: 5.35±0.54 mmol/l; skiers: 4.94±0.41 mmol/l; p<0.01; cyclists: 4.94±0.42 mmol/l; p<0.01). The concentration of serum albumin was also decreased in athletes, but the difference did not reach statistical significance (controls: 4.76±0.26 g/l; skiers: 4.71±0.22 g/l; p=0.384; cyclists: 4.68±0.22 g/l; p=0.393). Results of the present investigation demonstrate that values of laboratorytesting lying outside conventional reference limits calculated on sedentary populations might express physiological adaptations to regular and demanding physical aerobic activity, emphasizing the need for the estimation of reliable reference limits in elite and professional athletes, to avoid equivocal interpretation of results within clinical and anti-doping contests.

Erythropoietin

This article summarizes recent advances in understanding the production and action of the hormone erythropoietin (Epo) with respect to high altitude physiology and sports medicine. Hypoxia is the main stimulus for Epo gene expression. An O2-labile protein (hypoxia-inducible factor 1, HIF-1) has been identified that is hydroxylated and degraded under normoxic conditions but active in hypoxia, where it enhances Epo gene transcription resulting in elevated hemoglobin levels and O2 capacity of the blood. The stimulation of Epo production at lowered arterial O2 tension can be maladaptive, if erythrocytosis develops such as seen in high altitude habitants. Within physiological limits the aerobic power increases in parallel with blood O2 capacity. Therefore, some elite athletes have misused recombinant human Epo (rhEpo), which is a beneficial anti-anemic drug in clinical practice. Indirect and direct methods to detect rhEpo doping have been recently developed.

Reticulocyte analysis by flow cytometry and other techniques

Enumeration of peripheral blood reticulocytes is an essential part of the diagnosis and management of anemic patients, since the number of reticulocytes in the peripheral blood reflects the erythrocytic activity of the bone marrow. Reticulocyte enumeration using flow cytometric methodology is rapidly replacing the inaccurate, imprecise manual counting technique used in the past. This article explores the pathophysiology of the reticulocyte, the various means of counting reticulocytes, and the diverse clinical applications of reticulocyte data.

Sugar profiling proves that human serum erythropoietin differs from recombinant human erythropoietin

Erythropoietin (EPO) from sera obtained from anemic patients was successfully isolated using magnetic beads coated with a human EPO (hEPO)-specific antibody. Human serum EPO emerged as a broad band after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular weight slightly smaller than that of recombinant hEPO (rhEPO). The bandwidth corresponded with microheterogeneity because of extensive glycosylation. Two-dimensional gel electrophoresis revealing several different glycoforms confirmed the heterogeneity of circulating hEPO. The immobilized anti-hEPO antibody was capable of binding a representative selection of rhEPO glycoforms. This was shown by comparing normal-phase high-performance liquid chromatography profiles of oligosaccharides released from rhEPO with oligosaccharides released from rhEPO after isolation with hEPO-specific magnetic beads. Charge analysis demonstrated that human serum EPO contained only mono-, di-, and tri-acidic oligosaccharides and lacked the tetra-acidic structures present in the glycans from rhEPO. Determination of charge state after treatment of human serum EPO with Arthrobacter ureafaciens sialidase showed that the acidity of the oligosaccharide structures was caused by sialic acids. The sugar profiles of human serum EPO, describing both neutral and charged sugar, appeared significantly different from the profiles of rhEPO. The detection of glycan structural discrepancies between human serum EPO and rhEPO by sugar profiling may be significant for diagnosing pathologic conditions, maintaining pharmaceutical quality control, and establishing a direct method to detect the misuse of rhEPO in sports.

Hypoxia-dependent protein expression: erythropoietin

Normal cell homeostasis relies on the ordered flow of nutrients and substrates through metabolic pathways. Any perturbation of this flow eventually leads to dysfunction, impairment of defense mechanisms, loss of viability and death. High altitude and pathological hypoxia represent a serious and frequent cause for the loss of cell viability. Although organisms customarily respond by triggering adaptive or maladaptive mechanisms, all forms of life eventually succumb to hypoxia if it is severe enough, irrespectively of the primary cause. This paper reviews one of the mechanisms by which organisms respond to hypoxia: erythropoiesis. Although such response is not always beneficial, the discovery of the biochemical mechanisms underlying erythropoiesis has triggered an active field of research that is actually applying lessons learned in the mountains to a more clinical environment.

Identification of Blood Erythroid Markers Useful in Revealing Erythropoietin Abuse in Athletes

Recombinant human erythropoietin (rEpo) is being used with increasing frequency by endurance athletes to improve aerobic potential. Although rEpo administration has been banned by the International Olympic Committee, no methods are available to unequivocally detect its abuse in sports. Prompted by these considerations, we evaluated the main hematological and biochemical modifications measured in the blood of 18 volunteers upon rEpo administration. Different rEpo regimens, iron, folic acid, and vitamin B12 administration did not significantly modify the percentage increase in hematocrit. However, a significant decrease in circulating ferritin (fr) and an increase in the soluble transferrin receptor (sTfr) were not found in athletes receiving low (30 IU/kg) doses of rEpo. Thus, an increase in the sTfr/fr ratio cannot be used as an indicator of rEpo abuse, at least when the hormone is administered at low concentrations. In contrast, the amounts of beta-globin mRNA detected by quantitative competitive (RT)-PCR in whole blood samples significantly increased above the threshold levels in all of the treatments investigated. Taken together, these data suggest that hematocrit value, reticulocyte count, soluble transferrin receptor content, and concentration of beta-globin mRNA, when included in a new multiparametric formula, can detect rEpo abuse in 57.5% of the samples examined with a confidence interval of 99.99%. Thus, the method reported in this paper could significantly improve the tests currently available, which in similar experiments allowed the detection of rEpo abuse in only 7.6% of the samples examined.