Erythropoietin assays: some new and different approaches.

Published reports of the levels of erythropoietin (Ep) in normal human serum have been reviewed. Current evidence suggests that the level of Ep in normal human serum is 30 +/- 10 mU Ep/ml. When serum was concentrated before assay somewhat lower values were obtained and the mouse fetal liver cell assay gave slightly higher values. Three new potential Ep assay techniques are presented. These are: 1) The use of synthetic microbeads as indicators in an agglutination assay, 2) the use of wheat germ lectin in affinoelectrophoresis techniques, and 3) an immunoradiometric assay as an alternative to radioimmunoassays. The results indicate that the use of all three assays should be explored further.