Blood doping in athletes--detection of allogeneic blood transfusions by flow cytofluorometry

A SNP-based genotyping strategy to detect the abuse of homologous blood transfusion from dried blood spots

We performed genotyping analysis of human biallelic polymorphisms (single nucleotide polymorphisms) for the detection of homologous blood transfusion in sports doping. DNA was extracted from dried blood spots and quantified real-time fast PCR. The method was proven to allow the detection of transfusions up to a donor percentage of 1%, with a significant improvement in terms of sensitivity with respect to both the reference cytofluorimetric method and a previously proposed strategy based on the DNA STR-based strategy.

Evaluation of the detection of the homologous transfusion of a red blood cell concentrate in vivo for antidoping

Two doping cases of homologous blood transfusion (HBT) during Tokyo 2020 Summer Olympics have shown that more controls are needed. The method of detection using flow cytometry to evaluate the expression of minor blood group antigens from red blood cells (RBCs) and identify different RBC populations is efficient but still complex to perform with multiple antigens detection. Recently, the interest of using forensic DNA analysis was also highlighted as a potential new method to detect HBT, with possibility to start from dried blood spots (DBS) instead of fresh blood. After a first phase of development, a protocol was validated for HBT detection using DNA analysis after extraction from DBS. Presence of a second DNA was clear down to 2% of donor blood in vitro. A flow cytometry protocol was also developed with preparation and analysis in 96-well plates and detection of two different antigens per well using two secondary antibodies with distinct fluorophores. The objective of the project was to evaluate the window of detection of an HBT performed in vivo with 150 mL of RBC concentrate. Blood samples obtained over 7 weeks post-transfusion were analyzed. DNA profiling from DBS was not sensitive enough to detect the presence of a second DNA even 1 day after transfusion. On the contrary, the flow cytometry protocol was very efficient and allowed identification of several double populations of RBC (expressing/non-expressing several antigens) until day 50 post-transfusion. This protocol can be fully validated for a future application to doping control samples.

Minor red blood cell antigen phenotyping of athletes sampled in international competitions

Blood transfusion is performed by cheating athletes to rapidly increase oxygen delivery to exercise muscles and enhance their performance. This method is banned by the World Anti-doping Agency (WADA). Heterologous or allogenic blood transfusion happens when blood from a different person is transfused. The method used to detect this type of doping is based on flow cytometry, by identifying variations in blood group minor antigens present on the red blood cells' surface. Transfusion practices have regained interest since the introduction of human recombinant erythropoietin detection method. It has been reported that the number of occurrences of two athletes sharing an identical phenotype in the same sport was five times higher than the theoretical populational probability. The present work describes the prevalence of 10 erythrocytes surface antigens in a population of 261 athletes from all five continents. The matching phenotype per sport is also described.

Detection of Homologous Blood Transfusion in Sport Doping by Flow Cytofluorimetry: State of the Art and New Approaches to Reduce the Risk of False-Negative Results

This article presents the results of a study aimed to give new suggestions and strategies for improving the implementation of the flow cytofluorimetry-based method for the detection of homologous blood transfusions in doping control. The method is based on the recognition of the phenotypic mismatch between minority blood group antigens possessed by the donor and the recipient. Two strategies have been followed to reduce the risk of false-negative results: (i) the monitoring of a broader range of erythrocytes surface antigens; and (ii) the application of different surface erythrocyte staining protocols, tailored on the different antigens and the type of antigenic mismatch that had to be detected (whether it is the donor or the recipient who expresses or not the antigen to be detected). Special attention has also been focused on the time factor, to avoid prolonged sample storage, since hemolysis may have a significant impact on the reliability and quality of the results. Our experimental evidence suggests that the risk of false-negative results can be minimized by (i) the expansion of the antigen panel, with the inclusion of four additional targets; (ii) a more accurate selection of the gating area of the red blood cells; (iii) the choice of a better fluorochrome (alexa fluor 488) to be conjugated to the secondary antibody; and (iv) the implementation of different staining protocols depending on the nature of the double population to be detected (donor expressing vs. recipient non-expressing and vice versa). The combination of the above approaches allowed a significant reduction of false-negative results, assessed on samples simulating a homologous blood transfusion between two compatible subjects.

Blood doping: risks to athletes' health and strategies for detection

Blood doping has been defined as the misuse of substances or certain techniques to optimize oxygen delivery to muscles with the aim to increase performance in sports activities. It includes blood transfusion, administration of erythropoiesis-stimulating agents or blood substitutes, and gene manipulations. The main reasons for the widespread use of blood doping include: its availability for athletes (erythropoiesis-stimulating agents and blood transfusions), its efficiency in improving performance, and its difficult detection. This article reviews and discusses the blood doping substances and methods used for in sports, the adverse effects related to this practice, and current strategies for its detection.

Comparison of multiple red cell volume methods performed concurrently in premature infants following allogeneic transfusion

BACKGROUND

Study of the pathophysiology and treatment of anemia of prematurity is facilitated by direct measurement of red cell volume (RCV) utilizing microliter quantities of blood samples. Our objective was to compare concurrent measurements of multiple direct RCV methods in infants.

METHODS

Eighteen preterm infants receiving clinically indicated transfusions had concurrent flow cytometric determinations of RCV and 24-h red blood cell (RBC) recovery based on donor-recipient differences of biotin-labeled RBCs (BioRBCs), Kidd antigen mismatched RBCs, and fetal hemoglobin-positive (HbF(+)) RBCs. High-performance liquid chromatography (HPLC) was also used for measuring HbF and adult hemoglobin protein concentrations for the determination of RCV.

RESULTS

Concurrent RCV measurements using BioRBCs (18 and 54 µg/ml), Kidd antigen, and HbF flow cytometry were not statistically different compared with RCVs measured using the reference BioRBC density (6 µg/ml). By contrast, the HbF-HPLC method overestimated RCV by 45% compared with the reference method. All the methods demonstrated 100% 24-h posttransfusion RBC recovery (PTR24).

CONCLUSION

Because BioRBC, Kidd antigen, and fetal hemoglobin (HbF) flow cytometry are safe and accurate methods requiring <10 µl of patient blood for determining RCV and PTR24 in preterm infants, they can be useful in clinical and research studies of anemia and other conditions.

Red blood cell populations and membrane levels of peroxiredoxin 2 as candidate biomarkers to reveal blood doping

BACKGROUND

Blood doping represents one main trend in doping strategies. Blood doping refers to the practice of boosting the number of red blood cells (RBCs) in the bloodstream in order to enhance athletic performance, by means of blood transfusions, administration of erythropoiesis-stimulating substances, blood substitutes, natural or artificial altitude facilities, and innovative gene therapies. While detection of recombinant EPO and homologous transfusion is already feasible through electrophoretic, mass spectrometry or flow cytometry-based approaches, no method is currently available to tackle doping strategies relying on autologous transfusions.

MATERIALS AND METHODS

We exploited an in vitro model of autologous transfusion through a 1:10 dilution of concentrated RBCs after 30 days of storage upon appropriate dilution in freshly withdrawn RBCs from the same donor. Western blot towards membrane Prdx2 and Percoll density gradients were exploited to assess their suitability as biomarkers of transfusion.

RESULTS

Membrane Prdx2 was visible in day 30 samples albeit not in day 0, while it was still visible in the 1:10 dilution of day 30 in day 0 RBCs. Cell gradients also highlighted changes in the profile of the RBC subpopulations upon dilution of stored RBCs in the fresh ones.

DISCUSSION

From this preliminary in vitro investigation it emerges that Prdx2 and RBC populations might be further tested as candidate biomarkers of blood doping through autologous transfusion, though it is yet to be assessed whether the kinetics in vivo of Prdx2 exposure in the membrane of transfused RBCs will endow a sufficient time-window to allow reliable anti-doping testing.

Detection methods for autologous blood doping

The use of blood doping is forbidden by the World Anti-Doping Agency. Several practices, such as blood transfusions are used to increase oxygen delivery to muscles and all of them are highly pursued. In this regard, the development of accurate methodologies for detecting these prohibited practices is one of the current aims of the anti-doping control laboratories. Flow cytometry methods are able to detect allogeneic blood transfusions but there is no official methodology available to detect autologous blood transfusions. This paper reviews protocols, including the Athlete Biological Passport, that use indirect markers to detect misuse of blood transfusions, especially autologous blood transfusions. The methods of total haemoglobin mass measurements and the detection of metabolites of blood bags plasticizers in urine are reviewed. The latter seems to be an important step forward because it is a fast screening method and it is based on urine, a fluid widely available for doping control. Other innovative approaches to blood transfusion detection are also mentioned. A combination of the reported methodologies and the implementation of the Athlete Biological Passport is becoming a promising approach.

Blood transfusion in sports

Blood transfusion is an effective and unmediated means of increasing the number of red blood cells in the circulation in order to enhance athletic performance. Blood transfusion became popular in the 1970s among elite endurance athletes and declined at the end of the 1980s with the introduction of recombinant erythropoietin. The successive implementation in 2001 of a direct test to detect exogenous erythropoietin and in 2004 of a test to detect allogeneic blood transfusion forced cheating athletes to reinfuse fully immunologically compatible blood. The implementation of indirect markers of blood doping stored in an Athlete's Biological Passport provides a powerful means to deter any form of blood transfusion.

Red blood cell volume can be independently determined in vitro using sheep and human red blood cells labeled at different densities of biotin

BACKGROUND

The development of valid methods for repeatedly measuring red blood cell (RBC) volume (RCV) in the same individual would be useful in furthering understanding of the physiology and pathophysiology of the pregnant woman, fetus, and infant under a variety of conditions.

STUDY DESIGN AND METHODS

Small volumes (5 to 100 mL) of either sheep or human blood were used to test the hypothesis that there is no significant difference in RCV and blood volume determined in vitro using as many as five populations of RBCs labeled at distinct biotin densities. By varying the mass of biotinylating reagent, the density of biotin on the surface of RBCs was incrementally increased to produce discrete populations as assessed by flow cytometric enumeration. Calculation of RCV for each biotin-labeled RBC population was based on the dilution principle.

RESULTS

All biotin densities, except the most densely labeled, where variance was the greatest, accurately quantitated the in vitro blood volume to within 10 percent of the correct value. There was no bias of either overestimation or underestimation in the determination of the blood volume using either sheep or human RBCs.

CONCLUSION

These in vitro results provide evidence that the multidensity biotin labeling method is sufficiently accurate to utilize in vivo for repeated determination of circulating RCV and blood volume.

The analytical chemistry of drug monitoring in athletes

The detection and deterrence of the abuse of performance-enhancing drugs in sport are important to maintaining a level playing field among athletes and to decreasing the risk to athletes' health. The World Anti-Doping Program consists of six documents, three of which play a role in analytical development: The World Anti-Doping Code, The List of Prohibited Substances and Methods, and The International Standard for Laboratories. Among the classes of prohibited substances, three have given rise to the most recent analytical developments in the field: anabolic agents; peptide and protein hormones; and methods to increase oxygen delivery to the tissues, including recombinant erythropoietin. Methods for anabolic agents, including designer steroids, have been enhanced through the use of liquid chromatography/tandem mass spectrometry and gas chromatography/combustion/isotope-ratio mass spectrometry. Protein and peptide identification and quantification have benefited from advances in liquid chromatography/tandem mass spectrometry. Incorporation of techniques such as flow cytometry and isoelectric focusing have supported the detection of blood doping.