Polyclonal antibodies can be produced that reacts with recombinant EPO and its degradation products but not with native EPO. This antibody precipitation can be used to identify those glycopeptides that are uniquely reactive. These glycopeptides can be produced on preparative scale and used in the production of monoclonal antibodies which are screened against the original EPO and glycopeptides to select antibodies reactive to the specific glycopeptides an recombinant EPO but not to native human EPO. The monoclonal antibodies so selected are incorporated in a conventional ELISA and used to monitor urine and other bodily samples taken from athletes, either human or animal, and patients for presence and level of recombinant peptides or proteins. Alternatively, the polyclonal antibody can be used directly to produce ELISA tests.