Reticulocyte and haemoglobin profiles in elite triathletes over four consecutive seasons

Introduction: The World Anti-Doping Agency has implemented the Blood Passport in attempt to detect blood doping in athletes. The Blood Passport looks for uncommon changes overtime in reticulocytes percentage (Ret %), as a variable of the OFF-hr score, and haemoglobin concentration ([Hb]) reflecting potential doping violations. Few studies, however, have actually investigated the concurrent stability of Ret % and [Hb] in athletes over extended periods of time, none of which were measured in athletes who undergo strenuous and prolonged physical exercise. Methods: Measurements of Ret % and [Hb] were assessed over the course of four competitive seasons in elite triathletes (10 males and seven female). Blood was obtained at the start of the season, precompetitive period, competitive period and at the end of the competitive period. Results: Differences (P < 0.001) were observed in both [Hb] and Ret % between genders and there was a high variability between subjects. Neither males nor females exhibited differences in [Hb] across all periods within one season. Within gender, analysis revealed that Ret % varied significantly (P = 0.0018) between periods only in female athletes. Conclusion: We conclude that Ret % and [Hb] remain stable over four consecutive seasons in elite triathletes, confirming that both parameters are valid for antidoping purposes based on the Blood Passport. In addition, Ret % fluctuations within one season require further investigation in females.