The technique of using hexavalent chromium for labeling red blood cells in vitro was introduced by Gray and Sterling, in 1950.1 In 1953, Ebaugh et al.2 showed that this method was a convenient way to approximate the survival of erythrocytes in vivo. Weinstein and LeRoy 3 were the first to publish data on Cr51-labeled red cells from nine patients with various hematological disorders. Several other authors 4-6 have presented similar data from patients with known hemolytic disease. It remains necessary, however, to review critically the usefulness of this test in clinical practice as a measure of increased erythrocyte destruction.
It has been shown in the normal subject that the disappearance of the radioactivity from the blood results from at least two variables, the linear loss of the red cells from the circulation due to senescence and an exponential elution of chromium from the tagged cells.2,7