Differentiation of endogenous Erythropoietin and exogenous ESAs by Western blotting with deglycosylation

Doping tests for illegal use of erythropoiesis-stimulating agents (ESAs) have been developed. Here, we show a new Western blotting to distinguish endogenous erythropoietin (Epo, 35-38 kDa) and exogenous ESAs (epoetin alpha and beta; 38-42 kDa, darbepoetin alpha; 47-50 kDa, epoetin beta pegol; 93-110 kDa). In contrast, Liquid Chromatography/Mass Spectrometry analyzed all endogenous Epo and exogenous ESAs as delycosylated 22 kDa Epo, indicating that LC/MS analysis could not distinguish Epo and ESAs. We believe that our Western blotting is useful to protect against illegal use of ESAs.