Accounting For The ‘Dehydration Factor’ In The Athlete Biological Passport

Abstract

The Athlete Biological Passport (ABP) was implemented by the World Anti-Doping Agency in 2008 to monitor elite athletes for banned substances. The potential for dehydration to bias the ABP by elevating parameters such as hemoglobin (Hb) and hematocrit (Hct) deserves careful attention before integration into detection models. PURPOSE: To examine biological variation in euhydrated Hb and Hct for comparison against changes observed in response to a standardized loss of total body water (~3-4% body mass) achieved using two distinct types of dehydration. METHODS: Ten participants (7M, 3F; 23 ± 4 years) completed three days of controlled euhydration (EUH) from which the within-subject biological variation (CVw) and analytical variation (CVa) were used to estimate a meaningful change (unidirectional 95% level). Two trials of controlled dehydration via sweating (HYP) and diuretic administration (DIUR) followed. RESULTS: The CVw and CVa for Hb and Hct were both ~2% and 0.5%, respectively. When properly summed [RCV = 20.5 x 1.65 x (CVa2+CVw2)0.5] they explain a relative increase of ~5% (0.7 Hb units and 2.0 Hct units) between any two successive values measured 24 hours apart. Participants achieved body mass losses of 3.13 ± 0.44% (HYP) and 3.70 ± 0.54% (DIUR). The change in Hb was 0.6 units (HYP) and 1.4 units (DIUR) (P<0.05) vs EUH. The change in Hct was 2.1 units (HYP) and 4.2 units (DIUR) (P<0.05) vs EUH. Only with the diuretic was the change in Hb and Hct (1.4, 4.2) well beyond expected values due to biological variation (0.7, 2.0). CONCLUSION: Dehydration by ~3-4% of body mass produced changes in Hb and Hct beyond day-to-day variation (> unidirectional 95% level) only when achieved using a diuretic. These findings have important implications for claims made against dehydration as a bias factor in the ABP and also provide important insight related to hydration testing in general. Funded by USAMRMC; author views not official US Army or DOD policy.