Standardization of reticulocyte counts in the athlete biological passport: A practical update

Abstract

Introduction The athlete biological passport monitors blood variables over time to uncover blood doping. With the phasing in of a new series of blood analyzers, the Sysmex XN series, it was necessary to examine the comparability of results with the previously employed XT/XE series. A previous comparison between XN and XT/XE series suggested a small but significant bias between the two instruments in the measurements of RET%. Here, we examined the comparability of RET% on the XN and XT/XE platform using data collected over the first year since the transition. Methods The comparability of results obtained from XN and XT/XE instruments was assessed using three datasets: (i) 767 blood samples measured on both instrument series in 22 WADA‐accredited laboratories, (ii) 27 323 samples measured on either instrument across 31 laboratories, and (iii) 119 clinical samples and 110 anti‐doping samples measured on both instruments in a single laboratory. Results Analysis of the three datasets confirms the previous observation of a bias toward higher RET% values for samples measured on Sysmex XN instruments compared with the XT/XE series. Using data across a larger number of XN instruments and a larger athlete population, the current work suggests that the bias is proportional and slightly higher than previously observed across most of the range RET% values. Conclusion A model is proposed for the comparison of data across XN and XT/XE technologies whereby the instrument bias increases proportionally with RET% measured on Sysmex XN Series, but where the rate of increase is negatively related to IRF%.

Future opportunities for the Athlete Biological Passport

“…Variables analyzed by flow cytometry (with the Sysmex XN instruments generation since 2019) are now used for the measurement of the ABP hematological variables ( 10 ). Using a slightly modified technology for reticulocytes measurement compared to the previous XE and XT series ( 11 ), this latest generation of devices provides the quantification of many blood parameters currently not yet exploited by the ABP.…”

EPO and the athlete biological passport: Hematological results from a placebo‐controlled, boosting and microdose EPO administration in male recreational athletes

“…For the 12 participants in the EPO cohort, each participant Although not included as a primary or secondary marker in the ABP program, longitudinally monitoring the IRF% from an individual has shown promise especially since the switch to the Sysmex XN analyzer. [22][23][24] Therefore, individual changes in the IRF% from all participants in the EPO cohort (Figure S2) and placebo cohort (Figure S3) are presented as supplemental material.…”

Report of the International Council for Standardization in Haematology working group for standardization of reticulocyte parameters

“…Its value is in determining whether there is an erythropoietic response, and to differentiate hypoplastic anemias, hemolytic anemias and blood loss. More recently these parameters have been used in the detection of illegal blood doping in sports drug testing 1 . Automated reticulocyte analysis has advanced considerably since the days of manual enumeration of stained red cells containing ribosomes with a characteristic filamentous reticulin supravital staining pattern.…”

“…When the laboratory measurement procedures for an analyte are not standardized or harmonized the result is that laboratory methods may yield discordant results on the same sample. There is also evidence that a proportional, non‐linear bias of reticulocyte percentage and IRF can occur even with evolving technology from one manufacturer 1 . Not only does lack of standardization or harmonization potentially lead to discrepant results and inter‐laboratory bias, but it also reduces clinical utility.…”

“…More recently these parameters have been used in the detection of illegal blood doping in sports drug testing. 1 Automated reticulocyte analysis has advanced considerably since the days of manual enumeration of stained red cells containing ribosomes with a characteristic filamentous reticulin supravital staining pattern. The use of newer more specific nucleic acid stains and sensitive flow cytometric methods have led to significant improvements in analytical accuracy and precision of reticulocyte measurements, improved laboratory operational efficiency and the development of new clinical parameters for assessing other aspects of reticulocyte biology.…”