Effect of Repeated Oral Doses of Dexamethasone on the Hematological Passport used in Sports Drug Testing to Detect Blood Doping.

Background: Longitudinal monitoring of blood parameters is used in sports drug testing within the hematological module of athlete's biological passport to detect alterations that may indicate blood doping. Glucocorticoids (GCs) can act in an early stage of erythropoiesis stimulating the self-renewal of burst-forming unit erythroid and, therefore, might affect the hematological parameters.

Objective: The aim of the present work was to evaluate the impact of repeated oral doses of GCs on the hematological passport.

Methods: Dexamethasone (DEX) was administered to healthy volunteers using a multi-dose oral treatment (2 mg/12 h for 5 days, n = 8 males). A control group with 4 male volunteers that did not receive the DEX treatment was included in the study. Blood samples were collected on different days before administration to set baseline values and post-administration samples were collected up to day 8 from the first dose. All the parameters included in the hematological passport were measured using a Sysmex XN instrument and were used to estimate the hemoglobin mass and plasma volume using a multiparametric model. Variations in all parameters were statistically evaluated and compared to the physiological variations of the control group.

Results: A significant increase in reticulocyte-related parameters, along with a marked reduction in OFF-Score, was observed in the DEX group, particularly 48-72 h after the last dose. Hemoglobin concentration showed a transient decrease during the treatment, and ABPS exhibited isolated fluctuations without a consistent pattern. In contrast, hemoglobin mass remained stable throughout the study. The control group showed no relevant changes over time, with all hematological parameters remaining remarkably stable.

Conclusions: Our results show that multiple oral doses of DEX affect the erythropoiesis and, therefore, they can lead to atypical hematological profiles. Additional studies are necessary to evaluate the effect in hemoglobin longer after administration.