Relation between values of haemoglobin, erythrocytes and reticulocytes and body mass index in elite athletes of different sports disciplines

Sir, haematological parameters are used for monitoring health status of athletes, to prevent sports’ anaemia and also for suspecting blood doping. It is important to monitor professional athletes during the training and competitive season, because some modifications of the haematological parameters are induced from long-lasting and continuous exercise, although these variations are not usually clinically relevant and fall into reference intervals described for general population (Banfi et al., 2006a). Moreover, haematological parameters are integrated in formulae used in the antidoping context for screening the athletes. The reference intervals applied to athletes are usually those found in the general population. Athletes are thought to be physically normal and healthy by definition, but high training workload and psychophysical stress from competitions can modify their homeostasis, inducing apparently pathological biochemical and haematological results. In general, similar reference intervals for haematological parameters are described in athletes’ population and general population (Sharpe et al., 2002; Malcovati, Pascutto & Cazzola, 2003; Banfi et al., 2006a,b), but some differences exist (Lippi, Franchini & Guidi, 2002). Regardless of exercise and possible related effects, the reference intervals in athletes should take into account also the anthropometrical characteristics of the subjects, that can markedly differ among sports disciplines. We pointed out the need of considering body mass index (BMI) in evaluating and interpreting serum creatinine data in athletes, when a correlation between this parameter and BMI exists (Banfi, Del Fabbro & Lippi, 2006c). The relation between mass and haematological parameters has been not extensively studied. Therefore, we investigated the relation between haematological parameters and BMI in 126 top-level male athletes: 32 rugby players of Italian National team, nine triathletes of Italian National team, 27 football players of a Italian Second Division team, 24 cyclists of a ProTour team, 21 sailors of a America’s Cup yacht, 11 basketball players of a Italian First Division team, and two ice dancers of Italian National team. The age range was 17–35 years. The BMI was calculated as weight/(height) and supplied by teams’ physicians. Haematological parameters have been supplied by the automated system Abbott Cell Dyn 3700 (Abbott, Chicago, MI, USA). The blood drawings were performed at rest in the morning before the start of the training and competitive season. An informed consent for blood drawings has been obtained. The correlation between BMI and haematological parameters in the whole group of athletes gave significant result for erythrocytes (RBC; P 1⁄4 0.002), but not for haemoglobin (Hb) and reticulocytes (Ret). The correlation between mean values of the considered parameters in groups of athletes competing in different sports and BMI, gave non significant data (r < 0.1) for RBC and Ret, and a weak correlation for Hb (Figure 1). Haematological parameters are commonly used for monitoring athletes health status and performances, and also for suspecting the use of banned substances or procedures. The RBC mass is often considered the most important parameter for evaluating the training effectiveness (Gore et al., 1997). The RBC mass should be related to whole body mass, inducing also gender differences evidentiated by different reference intervals usually proposed for males and females (Van den Bossche et al., 2002). However, in athletes the gender difference on VO2max is principally related to the cardiac size, measured as left ventricular mass, accounting for 68.3% of the difference (Hutchinson et al., 1991). The lack of correlation between BMI and Hb in the whole group of athletes indicates that in a population with consistent number of subjects the body characteristics do not apparently influence the Hb concentration. A correlation between Hb and RBC with BMI has been described by Telford and Cunningham (1991), although reporting unclear BMI data. Similar findings are reported by Warrington et al. (2001) in tug-on-war and rugby athletes. When considering nonathletes population, Hb levels in pregnant women with BMI below 19 kg/m were significantly lower than for women in the higher BMI catLETTER TO THE EDITOR INTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY