Does body position during blood sampling influence the athlete biological passport variables?

Code: R19M02RF

Nearly 30 000 blood samples are collected yearly for the athlete biological passport (ABP). Therefore, accurate and precise measurement of blood variable with low bias are paramount to ensure the indirect detection and targeting potential of the ABP. The blood matrix as a suspension of living cells in plasma ensures oxygen transport to the working muscles thanks to the red blood cells. While circulation allows to maintain a constant composition of the blood, variations in the fluid balance may inevitably alter variables for which concentration values are reported (e.g., hemoglobin concentration ([Hb]) or hemotocrit (Hct)) while absolute measures (e.g., reticulocytes percentage (Ret%)) remain stable. In this context, numerous confounding factors affect blood variables and robust procedures are needed to limit pre-analytical variations of blood vaiables when analyzed for the ABP. Currently, the guidelines specify that 2h waiting is necessary after any physical exercise and require the athletes to be seated for 10 min before sample collection. The aim of this study is to investigate the influence of body position prior to and during phlebotomy (i.e. seated vs. supine) on blood variables reported in the ABP by collecting successive samples over 90 min in either position. Additionally, this study assesses if a short position change (e.g., walking a short distance from a waiting room to the sample collection site) influences the reading and may thus be acceptabe in the context of an antidoping blood sample collection sequence.

Main findings

The Athlete's Biological Passport (ABP) is a tool for the indirect detection of blood doping. Current guidelines from the World Anti-Doping Agency (WADA) require a delay of 2 hours after any physical exercise and to be seated for 10 minutes prior to any blood sampling to obtain a valid measurement.

Accurate and precise measurement of blood variables with low bias are paramount to ensure the indirect detection and targeting potential of the ABP. The blood matrix as a suspension of living cells in plasma transports oxygen to the working muscles. Variations in the fluid balance and thus plasma volume may inevitable alter variables for which concentration values are reported (e.g., haemoglobin concentration ([Hb]) or haematocrit (Hct)) while absolute measures (e.g., reticulocytes ercentage (Ret%)) remain stable.

Since body position prior to and during phlebotomy may influence the outcome, this study compared blood biomarker variations with changes in body position during blood sample collection. Ten successive venous blood samples from 38 subjects of 3 groups (elite cyclists, apnea divers and controls) in three situations (seated, after a 50 m walk, and supine) were collected and analyzed via flow cytometry. While reticulocytes percentage was unchanged in all conditions, haemoglobin concentration and hematocrit were stable after at least 10 min in a seated position. Due to shifts in plasma volume, the measure were significantly higher after changing posture for a short walk, but readjusted to previous levels after only 5 min. Supine position caused generally lower values after 10-30 min.

In conclusion, our study indicates that standing up shortly during an antidoping blood collection process (and walking up to 50 m to change seats for example) significantly alters the [Hb} and Hct values in athletes and healthy subjects. Values however stabilized after 5 min upon returning in a seated position. Blood sampled in a supine position may result in lower [HB] and Hct values that can affect an ABP profile. Blood samples for anti-doping purposes in the context of the ABP should therefore not be collected in a supine position. If a subject has to stand up shortly after having waited for 10 min (e.g., to change seat from a waiting room to the phlebotomy location), acceptable samples could be obtained after 5 min in a seated position. These findings can complement the current WADA guidelines for blood sampling in the context of the ABP.