is the biological passport effective at catching dopers?

the complexity, expense, and difficulty in testing for individual designer performance enhancing drugs means that athletes can often dope and evade detection, if they are somewhat intelligent in the way they administer the drug. in an attempt to combat the need to test for individual substances, for which chemists and pharmacists can continue iterating on - indefinitely, it would seem - the world anti-doping agency (wada) introduced the concept of the biological passport. the concept is rather simple if the implementation isn’t; if an athlete dopes, it will lead to hematological changes in various parameters that would be detectable and indicate an athlete is taking peds. however, the greatest strength of the passport is also its greatest weakness. the reference ranges which the passport uses are variable. that is, after an initial test, where hematological values are compared to population norms, the passport (or more accurately, the mathematics) will adjust for subsequent analysis.

as will be elucidated in a future post, there are different methods for administering peds. for example recombinant human erythropoietin (rhepo) can be used in smaller doses more frequently, a technique termed microdosing. for a number of reasons, this is the preferred method for administration in most athletes. so, researchers in australia asked the question: could athletes microdosing with rhepo be flagged by wada’s biological passport system.

in this particular study by ashenden et. al (2011), ten male subjects, consisting of various recreational endurance athletes underwent a five phase doping regime, where the dosages were steadily increased from 10 IU/kg to 40 IU/kg over a 10-12 week period. bloods taken each month were used for analysis with the athlete biological passport software. a future post will discuss the specific methods used for testing for rhepo, however this study used analysis of both hemoglobin and reticulocyte count, allowing a calculation of something known as an OFF score, a parameter that flags rhepo use often cessation of its use.

now, as mentioned before, the biological passport will adapt to previous assessments, after the initial sample is compared to thresholds from the population. so we can consider the mathematics used by wada and in this study:

after this first test, the predictive distribution will be iterative:

where res_n is the hematological parameter from sample ’n’.

to illustrate this in practice, the authors offered the following example for hb values of 134 g/l and 142 g/l for the first and second test respectively:

so, the second test will be based on iterative thresholds:

so, even though 142 g/l is significantly elevated above the baseline value of 134 g/l, it would not be flagged by the biological passport.

in short, the authors in this study found the same result in their investigation. the ten athletes were microdosing throughout the study and none were flagged by the system for either hb or off score, even though hb mean increased from 155.3 g/l to 164.3 g/l, representing an increase equivalent to infusing two blood bags. this means these athletes could have theoretically be doping in competition, and seeing positive benefits in their blood profiles and performances, and would not be caught by doping authorities.

using the biological passport is accompanied by urine tests, where direct testing for illicit substances can take place. the combination of these tests would have increased sensitivity, but the extra cost and inconvenience of these must be considered. indeed, only about a third of blood samples tested in the biological passport program in 2009 were accompanied by direct tests for urinary rhepo biomarkers.

in summary, it seems that even though the biological passport is a good step forward in doping control, it is far from the holy grail of testing that so many pundits make it out to be. athletes and their doctors understand the process described above, probably better than wada, and will therefore just alter the manner in which they dope so they will not be caught, just like athletes did in the 1990’s. for a more complete analysis of this study, please read the full article for the european journal of applied physiology.

stay tuned for more posts on rhepo and microdosing and testing protocols.

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references

ashenden, m., gough, c. e., garnham, a., gore, c. j., & sharpe, k. (2011). current markers of the athlete blood passport do not flag microdose epo doping. european journal of applied physiology, 111(9), 2307-2314.