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Erythropoietin and blood doping
N Robinson, S Giraud, C Saudan, N Baume, L Avois, P Mangin and M Saugy
Br. J. Sports Med. 2006;40;i30-i34
doi:10.1136/bjsm.2006.027532
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i30
SUPPLEMENT
Erythropoietin and blood doping
N Robinson, S Giraud, C Saudan, N Baume, L Avois, P Mangin, M Saugy
...............................................................................................................................
Br J Sports Med 2006;40(Suppl I):i30–i34. doi: 10.1136/bjsm.2006.027532
See end of article for
authors’ affiliations
.......................
Correspondence to:
M Saugy, Swiss
Laboratory for Doping
Analyses, Institute of Legal
Medicine, Lausanne,
Switzerland; martial.
saugy@chuv.ch
.......................
Objective and method: To outline the direct and indirect approaches in the fight against blood doping in
sports, the different strategies that have been used and are currently being used to fight efficiently against
blood doping are presented and discussed.
Results and conclusions: The paper outlines the different approaches and diagnostic tools that some
federations have to identify and target sportspeople demonstrating abnormal blood profiles. Originally
blood tests were introduced for medical reasons and for limiting misuse of recombinant human
erythropoietin (rHuEPO). In this way it became possible to prevent athletes with haematocrit levels well
above normal, and potentially dangerous for their health, competing in sport. Today, with nearly a decade
of blood testing experience, sports authorities should be familiar with some of the limitations and specially
the ability of blood tests performed prior to competitions to fight efficiently against the misuse of rHuEPO,
blood transfusion, and artificial haemoglobin.
E
rythropoiesis is part of the large process of haematopoiesis, which involves the production of mature cells found
in the blood and lymphoid organs.1 Haematopoiesis is
continuously required because of the normal turnover in the
cell populations in the blood and lymphoid organs. In the
normal adult human, the daily turnover of erythrocytes
exceeds 1011 cells. During periods of increased erythrocyte
loss, due to haemolysis or haemorrhage, the production of
erythrocytes increases rapidly and markedly. However, overproduction of erythrocytes does not occur, even after the
most severe loss of erythrocytes.
In haematopoiesis, a few pluripotent haematopoietic stem
cells in the bone marrow proliferate and differentiate to give
rise to all the cellular components of the blood and the
lymphoid system. During this process, an individual haematopoietic cell undergoes an apparently random process called
commitment. When a cell undergoes commitment, its
potential to proliferate becomes limited and its potential to
develop into multiple types of mature cell is also restricted.
Thus, these haematopoietic cells are termed committed,
lineage specific progenitor cells.
The major stages of differentiation in mammalian erythropoiesis are as follows. The most immature stage of
committed erythroid progenitors is the burst forming uniterythroid (BFU-E). The next major stage of erythroid
progenitor cell development is the colony forming uniterythroid (CFU-E). A continuum of erythroid progenitor
stages exists between the BFU-E and CFU-E, with decreasing
proliferative potential as the progenitors approach the CFU-E
stage. The descendant cells of the CFU-E are termed erythroid
precursor cells. These erythroid precursors are proerythroblasts, basophilic erythroblasts, polychromatophilic erythroblasts, and orthochromatic erythroblasts. The orthochromatic
erythroblasts do not divide, but they enucleate, forming the
nascent erythrocyte called the reticulocyte.
PRODUCTION OF ERYTHROPOIETIN
Erythropoietin (EPO) is a 30 400 molecular weight glycoprotein hormone produced mainly in the kidney, and also in the
liver (,10%) and, in very little quantities, in the brain.2–5 The
physiological stimulus for EPO production is tissue hypoxia,
which, in the large majority of instances, is directly related to
the number of circulating erythrocytes.6 Thus, EPO and
erythropoiesis are part of a negative feedback cycle that keeps
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tissue oxygen delivery within a narrow range by controlling
the number of erythrocytes circulating in the blood.7 ln a
normal individual, any loss of erythrocytes, such as by
bleeding or haemolysis, decreases delivery of oxygen to the
tissues.8 When this tissue hypoxia is sensed by cells in the
kidney and liver capable of producing EPO, they produce and
secrete EPO into the plasma.9 EPO is carried to the bone
marrow, where it binds to specific cell surface receptors on its
target cells—the CFU-E, pro-erythroblasts, and basophilic
erythroblasts.10 11 The binding of EPO by these cells increases
their ability to survive and reach the reticulocyte stage and
thereby contribute to the population of circulating erythrocytes. The increased numbers of circulating erythrocytes in
turn deliver more oxygen to the tissues. This increased
oxygen delivery is sensed by the EPO producing cells, which
then reduce EPO production so that the normal steady state
number of erythrocytes is restored.
The response of the kidneys to hypoxia has been shown to
be exponential12—that is, in individuals with a normal
capacity to produce EPO, a linear decline in haematocrit is
accompanied by an exponential increase in plasma EPO
levels. This exponential increase is not based on the release of
stored, preformed EPO. Rather, the hypoxia is sensed by an
intracellular molecule that interacts with an enhancer
element of the Epo gene and thereby induces transcription
of the gene.13 The increase in EPO production in the hypoxic
kidney is achieved by recruitment of more cells to produce
EPO. The EPO producing cells of the kidney are a minor
subset of cortical interstitial cells. Under normal conditions,
only a few scattered cells produce EPO. When a threshold
level of hypoxia is achieved, the cells capable of producing
EPO do so at a maximal rate. The greater the areas of renal
cortex in which the hypoxia threshold is met, the greater the
number of cells that produce EPO.9
MECHANISM OF ACTION OF ERYTHROPOIETIN
ln the bone marrow, EPO binds to receptors displayed on the
cell surface of CFU-E, proerythroblasts, and basophilic
erythroblasts. The mature EPO receptor, with a molecular
Abbreviations: BFU-E, burst forming unit-erythroid; CFU-E, colony
forming unit-erythroid; EPO, erythropoietin; IOC, International Olympic
Committee; LAD, Swiss Laboratory for Doping Analyses; rHuEPO,
recombinant human EPO; sTFR, soluble transferring receptor
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Erythropoietin and blood doping
i31
weight of approximately 72 000, is a transmembrane
glycoprotein, a member of a much larger family of receptors
of cytokines and haematopoietic growth factors. The effect of
EPO binding to its receptor, in terms of cellular physiology,
has been shown to be the prevention of programmed cell
death (apoptosis).14 15 In multiple systems of erythropoiesis,
EPO has been shown to be a survival factor for the erythroid
cells in the later stages of differentiation from the CFU-E
through basophilic erythroblasts. Although an effect of EPO
on mitosis has been reported for BFU-E and an EPO
dependent cell line, EPO is required only for CFU-E and
later stages, and apoptosis appears to result when EPO
signalling cannot occur.
DETECTING rHuEPO MISUSE IN SPORTS
The availability of recombinant human EPO (rHuEPO) in
1987 in Europe made it clear that this ergogenic hormone
would be used illicitly in endurance sports. Therefore, the
International
Olympic
Committee
(IOC)
Medical
Commission decided to ban this drug in 1990, even though
all forms of blood doping had been officially banned since
1984. Two philosophies were developed for the detection of
rHuEPO misuse in sports. The first one was based on the
detection of indirect blood markers and the second one was
based on the direct detection of rHuEPO in urine.16 The
promotion of secondary blood markers was mainly on the
basis that they could be used to detect rHuEPO injected a
long time ago (more than a week ago), and also that they
could be used to detect all kinds of erythropoietic stimulator
such as erythropoietin alfa, beta, omega, and delta, and
darbepoetin alfa and mimetic peptides.17 18 Furthermore,
secondary blood markers could eventually be used to identify
athletes who ceased using rHuEPO or other erythropoietic
stimulators. In the meantime, scientists were working on the
direct detection of rHuEPO in blood or urine. This latter
method had the advantage of identifying the drug itself (or
metabolites), but had the disadvantage of being expensive,
little sensitive, and delicate to perform.
Mean Hct
Mean Reti
55
On
Off
3.3
53
2.9
51
2.5
2.1
47
1.7
45
1.3
43
0.9
41
Iron
39
Reti (%)
Hct (%)
49
0
rHuEPO
0.5
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75
Days
Figure 1 Model showing the profile of mean haematocrit (Hct) and
reticulocyte count (Reti) (standard error of mean) during continuous
recombinant human erythropoietin (rHuEPO) treatment with regular
intravenous iron injections (see vertical bars near the x axis). The study
included three periods: baseline, treatment (ON) and post-treatment
(OFF). The horizontal line represents a theoretical cut-off limit to
determine which urine samples should be collected to confirm rHuEPO
misuse.
Figure 2 Anti-doping urine analysis demonstrating the presence of
recombinant human erythropoietin (rHuEPO) in urine (see lane 4). Lane
1: rHuEPO standard; 2: positive urine (control); 3: negative urine
(control); 4: sample declared positive; 5: darbepoetin alfa (Aranesp
standard).
Indirect methods of detection
In 1993, with the introduction of sophisticated haematological analysers some scientists proposed a model implicating
the analysis of the percentage of red blood cells having a
haemoglobin concentration below 28 pg (mean corpuscular
haemoglobin (MCH)) and a volume above 128 fl (mean
corpuscular volume (MCV)). These red blood cells were called
macrocytic hypochromatic erythrocytes. This test had the
advantage of being fast and cheap (as long as the laboratory
was equipped with this special analyser) and was highly
selective. Unfortunately, the test was limited by its relatively
poor sensitivity; 50% of the rHuEPO samples were not
detected.19
Another indirect test, developed in 1996 for the detection
of rHuEPO misuse, was based on the determination of the
soluble transferring receptor (sTFR)/ferritin ratio.20 The
results of a trial involving healthy subjects demonstrated
that regular rHuEPO injections significantly increased the
sTFR concentration. Ferritin was used as a denominator
mainly to prevent variations in hydration level.
Unfortunately, during this trial, the ferritin levels of the
subjects collapsed because they did not receive any iron
supply. As iron supplementation is a common practice among
athletes (specially intravenous iron injections),21 the sTFR/
ferritin ratio was modified into a new ratio taking into
account the possible exercise induced haemoconcentration,
the sTFR/total protein.22
The lack of sensitivity of some of the secondary blood
markers as well as the lack of specificity of others encouraged
some scientists to put them together in a multiple markers
mathematical model to discriminate rHuEPO misusers from
healthy sportspeople. Following a double blind study with
regular rHuEPO injections (continuous treatment), the
Australian Institute of Sport, together with the Australian
Sports Drug Testing Laboratory, designed an anti-doping test
using multiple secondary blood markers such as the
haematocrit level, the reticulocyte haematocrit, serum sTFR
and EPO concentrations, and lastly the percentage macrocytic
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i32
Robinson, Giraud, Saudan, et al
A
Figure 3 Anti-doping blood analysis
demonstrating the presence of a single
(A, B) or mixed (C, D) red blood cell
population(s). A: single population
without expression; B: single population
with expression; C: mixed population
with a majority expressing; D: mixed
population with the majority non
expressing. FITC, fluoroscein
isothiocynate.
B
552
566
100
101
102
103
100
FITC
101
102
103
102
103
FITC
C
D
457
465
100
101
102
103
100
FITC
cells. Different mathematical models were developed allowing the identification of sportspeople under rHuEPO treatment (ON-model) and those who had taken rHuEPO in the
past (OFF-model).23 In August 2000, the IOC Medical
Commission approved the ON-model to be used during the
2000 Olympic Games in Sydney. As the direct method
capable of discriminating endogenous EPO from rHuEPO
had already been published in spring 2000,24 the ON-model
was used only as a screening test to determine which urine
samples had to be collected to perform the urinary test.
At the same time that the above mentioned study was
performed in Australia, the Laboratoire Suisse d’Analyse du
Dopage (Swiss Laboratory for Doping Analyses; LAD)
conducted a similar randomised controlled, double blind
trial, except that iron supplementation was given much more
importance and it was given intravenously—for maximum
efficiency and to be as close as much as was possible to what
is done in cycling. The results showed that the behaviour of
secondary blood markers was different during the continuous
treatment. In contrast with the Australian study, the Swiss
study demonstrated that some of the secondary blood
markers (haematocrit, haemoglobin, and reticulocyte count)
could be used as part of a screening test, but in no case could
be used for anti-doping purposes (fig 1).25
Direct methods of detection
Endogenous EPO and rHuEPO are slightly different, and
these differences are certainly because the glycosylation of
rHuEPO takes place in Chinese Hamster Ovary (CHO) cells
rather than in human cells.26 Indeed, the post-translational
modifications are species and tissue dependent and also
dependent on the cell culture conditions. Therefore, it is
possible to separate the endogenous from the exogenous EPO
isoforms based on the differences in the charge status of
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101
FITC
different sugars.27 28 The technique developed by Wide
allowed the separation of the various isoforms thanks to
the differences in charge status of the different sugars. Is was
shown that this technique was reliable in urine and in blood
as long as the biological samples were collected within
24 hours after the last rHuEPO injection. Unfortunately, once
the rHuEPO treatment had ceased for more than three days,
less than 50% of the treated subjects could be declared
positive. Seven days after the last rHuEPO injection, none of
the samples showed any traces of rHuEPO.29 30
A few months before the 2000 Summer Olympic Games in
Sydney, the French anti-doping laboratory in Paris published
in Nature a novel test based on isoelectric focusing patterning
and a double blotting protocol.24 As the exogenous isoforms
of rHuEPO are less acidic than the endogenous EPO, it was
possible to develop a convenient protocol to separate them
using the isoelectric focusing method. This test was designed
to separate alfa, beta, and omega rHuEPO as well as
darbepoetin alfa (see fig 2).31 32
TARGETING rHuEPO MISUSERS
The LAD and the some federations took the decision together
to launch the blood screening test based on the determination of the haematocrit, the haemoglobin and the reticulocyte
count. It was introduced during the 2001 cycling season, Tour
des Flandres.33 Very soon it was demonstrated that blood test
was capable of identifying rHuEPO misusers.23 34–36 Since
then, quite a few other sports federations have decided to
introduce the screening test set up in Lausanne. With time,
this test was shown to be even more efficient during a follow
up of the athletes (blood profile), and variations above
normal were shown to be excellent indicators of blood
manipulation. In fact some models take these variations into
account, and athletes demonstrating variations above their
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Erythropoietin and blood doping
i33
What is already known about this topic
What this study adds
Blood doping has been common practice in some endurance
sports for quite a few decades, because its efficiency has
clearly been demonstrated. In the early 1990s, rHuEPO was
launched on the market. As a side effect of this blood doping
became even more attractive. For that reason, some
international sports federations had to limit and fight against
blood doping, notably by analysing blood markers of altered
erythropoiesis, such as haematocrit, haemoglobin, and
reticulocyte count. Finally in 2000, a direct detection test of
rHuEPO in urine was introduced which enabled demonstration of the origin of EPO.
Since the introduction of rHuEPO on the market, quite a few
strategies have been elaborated to fight blood doping. This
review describes the strategies, their limitations, and their
potential to fight blood doping more efficiently, notably
homologous blood transfusion.
individual reference range are targeted and have to go
through appropriate urine and blood anti-doping tests.37
ABNORMAL BLOOD PROFILES
For approximately two years, abnormal blood profiles have
been noticed without any traces of rHuEPO in urines.36 This
meant that athletes were either doping with undetectable
compounds or had returned to ‘‘old’’ doping techniques, such
as blood transfusion. Blood transfusion to enhance oxygen
transport with the increase of red blood cell mass was
common practice in the early 1970s.38 This way of doping
virtually disappeared with the arrival of rHuEPO on the
market at the end of the 1980s, because it is much easier to
use the hormone (easy to store and to use). The launching in
2000 of the direct detection test of rHuEPO in urine samples
had a disadvantage—a return to blood transfusion. The
regular follow up of blood markers such as haematocrit,
haemoglobin, and reticulocyte count suddenly showed that
some athletes had abnormal values of blood markers
although rHuEPO could not be detected in urine. This clearly
indicated a return to blood transfusion practices. With the
possibility of analysing specifically the red blood cell
membrane proteins defining notably the different blood
groups and subgroups, the LAD decided to perform for the
first time anti-doping tests in blood (summer 2004) (fig 3).
The specific labelling of some red blood cell membrane
proteins in combination with flow cytometry proved that
abnormal blood profiles were due to homologous blood
transfusion.39 Thus the disadvantage of anti-doping tests is
that some sportspeople change their doping habits, notably
they recourse to autologous blood transfusion. This method is
for the time being undetectable, but the policy of ‘‘No Start’’
introduced by some federations will strongly limit the
efficiency of this doping strategy (see reference 37).
The appropriate way to fight blood doping is to establish
for each marker and measure (haematocrit, haemoglobin,
OFF-score, reticulocyte count) individual reference values.37
In this way it will not be necessary to take into account the
sex, ethnic origin and the kind of sport practised. Each person
has his or her own set reference values and based on
variations and evolution of the markers over time, it is
possible to identify those athletes who are manipulating. This
is certainly the best way to fight blood doping as long as the
preanalytical and analytical conditions are optimal. The
approach improves even more when announced and unannounced blood data are put together, because data of athletes
manipulating their blood at the time of announced blood
controls will show discrepancies. Eventually, in the future, a
policy of ‘‘No Start’’ for all athletes demonstrating abnormal
blood values could be a solution to limit the costs related to
the elaboration of specific anti-doping tests for all imminent
molecules/methods and will nevertheless limit the misuse of
blood doping.17 18 40
CONCLUSIONS
Sports federations that have introduced blood tests actually
have a powerful tool to follow all athletes potentially
misusing rHuEPO or blood transfusion. The anti-doping tests
need to be focused mainly on those demonstrating abnormal
blood data. This targeting will also enable the federations to
determine the prevalence of doping methods before any
validated anti-doping test is introduced on the market. This
was the way in which it was found out that haemoglobin
based oxygen carrier (HBOC) misuse was not a major
problem.
.....................
Authors’ affiliations
N Robinson, S Giraud, C Saudan, N Baume, L Avois, P Mangin,
M Saugy, Swiss Laboratory for Doping Analyses, Institute of Legal
Medicine, Lausanne, Switzerland
Competing interests: none declared
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