Yearly intrasubject variability of hematological biomarkers in elite athletes for the Athlete Biological Passport

Confounding factors including exercise and environments challenge the interpretation of individual Athlete Biological Passports (ABPs). This study aimed to investigate the natural variability of hematological ABP parameters over 1 year in elite athletes compared with healthy control subjects and the validity of a multiparametric model estimating plasma volume (PV) shifts to correct individual ABP thresholds. Blood samples were collected monthly with full blood counts performed by flow cytometry (Sysmex XN analyzers) in 20 elite xc‐skiers (ELITE) and 20 moderately trained controls. Individual ABP profiles were generated through Anti‐Doping Administration & Management System Training, a standalone version of the ABP's adaptive model developed by the World Anti‐Doping Agency. Additionally, eight serum parameters were computed as volume‐sensitive biomarkers to run a multiparametric model to estimate PV. Variability in ELITE compared with controls was significantly higher for the Abnormal Blood Profile Scores (P = 0.003). Among 12 Atypical Passport Findings (ATPF) initially reported, six could be removed after correction of PV shifts with the multiparametric modeling. However, several ATPF were additionally generated (n = 19). Our study outlines a larger intraindividual variability in elite athletes, likely explained by more frequent exposure to extrinsic factors altering hematological biomarkers. PV correction for individual ABP thresholds allowed to explain most of the atypical findings while generating multiple new ATPF occurrences in the elite population. Overall, accounting for PV shifts in elite athletes was shown to be paramount in this study outlining the opportunity to consider PV variations with novel approaches when interpreting individual ABP profiles. This study outlines a larger intraindividual variability in elite athletes for hematological biomarkers included in the Athlete Biological Passport (ABP). Increased occurrences of atypical variations in blood parameters were observed in elite athletes, likely caused by plasma volume shifts. A better assessment of confounding factors and the development of innovative approaches to estimate plasma volume variations should be pursued.