Detection of a Distinct Erythropoietin (EPO) Profile After Isoelectric Focusing in Patients With Familial Erythrocytosis

Since the implementation of the first erythropoietin (EPO) detection method to fight the use of recombinant EPO (rEPO) for doping, the techniques used and identification criteria have evolved. The first technique involved iso-electric focusing (IEF-PAGE) to separate EPO isoforms by their charges. It can still be used for initial testing but is now largely replaced by electrophoretic separation based on molecular weight (SDS-PAGE or SAR-PAGE) to conclude decisively on the presence of rEPO. Recently, different mutations in the noncoding region of the EPO gene were identified in patients with familial erythrocytosis. Their blood EPO profiles after IEF-PAGE were very basic and in the same area as rEPO. To avoid any possible misinterpretation in an antidoping context, the goal of this work was to characterize urine and blood EPO profiles from these patients using all methods authorized in antidoping laboratories (IEF-PAGE, SDS-PAGE, and SAR-PAGE) and to compare them with wild-type (WT) EPO and with profiles obtained after the administration of rEPO Eprex. Results showed that SDS-PAGE and SAR-PAGE profiles were not modified in the patients compared with WT EPO and could not be mistaken for the presence of rEPO. In contrast, the IEF-PAGE profiles in urine were slightly more acidic than in blood and closer to the rEPO profile. However, they did not meet the identification criteria used when this technique was the only authorized method. It is highly unlikely that these EPO mutations, only identified in erythrocytosis patients yet, could lead to an adverse analytical finding.