Determination of human erythropoietin by radioimmunoassay. Method and clinical data.

A sensitive competitive radioimmunoassay for the determination of circulating human erythropoietin (Epo) is presented. This RIA of human Epo is founded on the extensive application of a recombinant protein approach. Thus, highly purified recombinant human Epo is employed both as a tracer, immunogen and occasionally as standard in the RIA. The lower limit of detection is approximately 8 mU/ml and well below the mean value of Epo in normal individuals (25.6 +/- 6.6 mU/ml). The intra- and interassay variation are 6.3 and 9.2%, respectively. The documentation of consistent alterations in Epo plasma levels of selected categories of anemic patients establishes the clinical relevance of the immunoassay. The radioimmunoassay of human Epo fulfills reasonable requirements of a clinical routine analysis in terms of both specificity, sensitivity and practicability.