Serum Erythropoietin Levels by Radioimmunoassay in Polycythaemia

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Abstract
A radioimmunoassay (RIA) method for erythropoietin (Epo) was developed and validated against the polycythemic mouse assay. The correlation was good, with a r = 0.94. Several other criteria of specificity were also filled by the RIA, which had a lower detection limit of 5 mU/ml. The mean [M] serum-Epo level in 6 patients with secondary polycythemia, 50.2 .+-. 26.2 mU/ml, was significantly higher than in a group of 11 normal subjects, 28.7 .+-. 7.2 mU/ml (P < 0.0002). The Epo level in 31 polycythemia vera (PV) patients, M = 21.9 .+-. 6.6 mU/ml, was not significantly different from normal (P = 0.006). Epo levels were measured before and after heat treatment and concentration of samples from normals and polycythemics. The levels of immunoreactive material increased after heat treatment and 40 times concentration in samples from normals and patients with secondary polycythemias, but decreased in PV. The Epo levels in serum in the low range measured by the new and previous RIA probably are not true Epo levels but are partly due to an unspecific serum effect that was removed by heat treatment.