The red cell chromium elution rate in patients with some hematologic diseases.

By M iiTIN J. CLINE AND NATHANIEL I. Bi ur. G RAY AND STERLING demonstrated that red cells can bind radioactive sodium chromate ( Na2 Cr51O4 ) in vitro rapidly and without apparent damage to the exposed cells.’ The chromium-51 labeling technic was rapidly adopted for the measurement of total red cell volume and red cell life span.26 As an erythrocyte label it possesses the advantage that it is not reincorporated after release from labeled cells. In addition, the method is simple, quick, and versatile. However, the Cr5’ label disappears from the circulation at a more rapid rate than can be accounted for solely on the basis of red cell destruction. This phenomenon has been attributed to elution of the label from intact surviving cells. Evidence has been presented by several investigators that the rate of the elution of Cr is probably an exponential function.2’3’5 We have been able to find 16 reported estimates of the elution rate based on independent measurements of red cell life span with the Ashby technic and on a correct mathematical analysis.3’57 The reported range of elution rates is 0.57 to 1.28 per cent per day in 12 normal individuals, and 1.0 to 1.51 per cent per day in four patients with hemolytic disease. On the basis of this limited number of determinations, an assumed elution rate of 0.9 to 1.0 per cent per day has frequently been used in calculating red cell life span from Cr51 data. Since Cr5’ red cell survival studies are usually performed in patients who have hematologic disease rather than in normal individuals, a larger number of determinations of the chromium elution rate in disease states would be of value.