Soluble transferrin receptor values in top level soccer players and skiers: comparison with sedentary people and pitfalls of laboratory methods

Aim. Hematological assessment is crucial in athletes: the risk of sports' anemia should be monitored with hematological parameters and iron metabolism tests. The aim of this study was to evaluate soluble transferrin receptor (sTfR) efficacy, as it is highly sensitive and specific and usually utilized in sport medicine for monitoring iron metabolism. Methods. sTfR was studied using two immunological methods (IDeA Orion, and Biokit) on a group of professional athletes, together with hematological and iron metabolism parameters. Values have been compared with those of sedentary people, before and during competitive season. Athletes were 76 professional male soccer players plus 20 males and 14 females of the alpine ski Italian National Teams. Results. The sTfR values in athletes are similar to those found in sedentary people. Different results have been observed between the two different methods: a bias of 0.37 mg/L was found comparing them. A significant correlation between sTfR and iron, transferrin saturation, and reticulocytes was found in skiers; there was no correlation with hemoglobin, erythrocytes, ferritin. In soccer players significant differences have been retrieved among different teams' distribution of data. Conclusion. The principal limit for using sTfR in sports medicine, but also in the general population, is the lack of standardization among methods. The quantitative differences in athletes between the two methods are high, although the behavior of the parameter is similar from the quality point of view. The differences between measured concentrations could influence the thresholds used in antidoping context.