Application of a modified INCSTAR Epo-trac 125/RIA for measurement of serum erythropoietin concentration in elite athletes

Abstract Objectives: To evaluate the analytical performance of a radioimmunoassay for measurement of erythropoietin. Design and Methods: The INCSTAR Epo-trac 125 I radioimmunoassay was examined for applications requiring sensitivity and precision within the normal range. Results: Sensitivity was improved by increasing sample volume to 300 μL. Minimal detectable concentration was determined at 5.3 U/L, %CV ranged from 4.8 - 5.8 and 13.3 - 6.4 for intra- and inter-assay imprecision, respectively. Accuracy was maximized by controlling for lipemic and hemolyzed samples and ensuring serum was separated from the clot within 1 h of collection. Values demonstrated good correlation to the Diagnostic Systems Laboratory RIA-kit. Conclusions: With sample volume increased to 300 μL and control of sample preparation, the INCSTAR Epo-trac 125/RIA showed improved precision. Assay sensitivity at lower values allows resolution of changes in erythropoietin within the normal reference range. Age was not found to influence erythropoietin concentration. Within 10 days sojourn at moderate altitude an increase in circulating erythropoietin and reticulocytosis was observed in swimmers.