Hemoglobin and hematocrit are not such good candidates to detect autologous blood doping

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In a recent manuscript published in the International Journal of Hematology, Sallet et al. [1] reported absolute norms of variation established for a maximal 15 days period to distinguish autologous blood transfusion from normal modifications, using hematocrit (Ht), hemoglobin ([Hb]) and stimulation index (Off-hr) (calculated using the following equation [Hb] – 60H reticulocytes in %) as markers. The thresholds the authors proposed are 6% for Ht, 4% for [Hb] and 20% for Off-hr. Although we grant this team for setting up new parameters to fight against blood doping, the application of the indirect detecting methodology for blood doping based on maximal variation of Ht, [Hb] and Off-hr requires additional considerations. We are concerned about the method used by the authors to establish the norms to tease out the ‘‘abnormal’’ variation. First, we are wondering how this norms based on the highest blood variations drawn from a group of 7 subjects with only 4 submitted to moderate altitude during 7 days can be statistically representative of physiological maximal variation of a ‘‘normal’’ population. Moreover, based on the literature defining good and bad responders [2], some more caution should be taken in the interpretation of the results. In addition, we believe that the conclusion of this study might lead to a type I error (i.e. false positive result) and that the norms proposed are likely ranged within the physiological values. That is why we disagree when the authors claim that ‘‘the absolute norms of variation of strictly above 6% for hematocrit; 4% for hemoglobin concentration and 20% for the stimulation index, from two blood samples spaced at an interval of maximum 15 days, were established in such a way as to detect autologous blood transfusion and distinguish an ‘abnormal’ variation’’. For the authors of the present paper [1], the purpose of using altitude exposure is to obtain a natural stimulation of the erythropoiesis allowing them to compare with the effects of the autologous transfusion. Unfortunately, as attested by their results, the hypoxic stimulus they used was rather mild and did not elicit any alteration in the measured parameters. We think that a more severe stimulus even using intermittent hypoxia would have been more appropriate first as a comparison point and second to stick with what is broadly used by the athletes. Indeed, in a study involving elite endurance runners submitted to an intermittent hypoxic training (living high–training low), we reported 5.7% increase in Ht in average after 6 days of exposure at 2,500 m during the nights (H3000) [3]. If we examine our data individually between the baseline and H3000, 2 of our subjects expressed Ht, [Hb] and OFF-hr higher than the ‘‘abnormal’’ of variation proposed by Sallet al. [1]: Ht: ?8.1%, [Hb]: ?9.7% and OFF-hr: ?20.5% V. Pialoux R. Mounier Laboratoire de Biologie des Activites Physiques et Sportives, Faculte de Medecine, 63000 Clermont-Ferrand, France