I briefly discussed this article in a previous blog, but I thought it would be worth sharing it in more detail as it is freely available to read online. Also it was published after my book went to print so it is not discussed there. It is written for a scientific audience but I think it is not too difficult to follow for the intelligent layperson.
You can access it at: http://onlinelibrary.wiley.com/doi/10.1111/j.1476-5381.2011.01822.x/full
The author is Carsten Lundby from the University of Zurich. It is a rather depressing summary of our state of play in detecting blood doping. Testing is especially tricky when the doping uses autologous blood i.e. an athlete pre-stores their own blood for a later transfusion. To counter this some sports, notably professional cycling, require athletes to have “blood passports”. The passport includes data from regular blood samples that have been taken to look for anomalous findings. These can include increases in red blood cell content (indicating a recent infusion of blood to aid performance) or increases in immature red blood cells (a likely consequence of a recent removal of blood to be stored for later use). A likelihood of doping score is calculated. But, as Lubdby stresses, this is not foolproof.
A recent study by Torben Pottgiesser at the University Hospital in Freiburg looked at control subjects who underwent a season’s blood doping program as if they were elite cyclists. Setting the probability level to 99% only caught eight out of eleven “cheats”. Setting the level to 99.9% only caught five. The danger of false positives is the problem here i.e. a positive test being triggered for someone who is not doping. Even setting the limit at a supposed 99.9% level, one test participant was initially “caught” who did not receive transfusions. On closer inspection the anomaly that lead to this false positive could be rationalised. But the lesson is clear. This data needs to be interpreted very carefully. This does not just require people trained in haematology, but also people who know the kind of tricks athletes use to avoid doping. It is therefore not surprising that, as outlined in my book, decisions to convict an athlete on an anomalous blood passport alone are likely to be appealed and ultimately decided in court.
For the curious, Figure 3 in the Lundby paper is one of the rare published examples of a doper’s diary; in this case a professional cyclist who was targetting success in a seven day race in March (Paris-Nice), a one day spring classic in late April, the three week Tour de France in July and the one day world championship race held in October. This makes salutary reading though we should not be surprised. Professional athletes take a scientific approach to all their preparations and drugs are surely no different.