De IAAF heeft wat antwoorden.
http://www2.iaaf.org/TheSport/Science/NSA15_1/Bibliography.html

En recombinant, ja EPO wordt al zo gemaakt. Maar dat lost niet alle problemen op:

It is quite common to find that recombinant human proteins made in non-human cells have somewhat different glycosylation patterns even though the protein (i.e. amino acid) sequences are identical. The “machinery” that glycosylates the protein is a little bit different in different species, and it makes slightly different oligosaccharide structures which are eventually attached to the protein. These structures are not controlled by the gene for Epo (or whatever), so they are characteristic of the host species, not the original human protein.

So if the recombinant product is made in big tanks of, say, hamster cells, it will have a different “hamster-style” glycosylation pattern that will show up on isoelectric focusing or capillary electrophoresis.