Editorial Retrospective

IN 1977, Stockman et al. measured erythropoietin levels in the plasma of 45 premature infants by means of a radioimmunoassay developed in the laboratory of Dr. Joseph Garcia.1 They found that the hemoglobin concentration or the oxygen-releasing capacity of the blood of premature infants correlated only roughly with the plasma erythropoietin content. They also found that fetal hemoglobin had only a slight influence on erythropoietin content. They concluded, however, that "factors that modulate the affinity of hemoglobin for oxygen are important in determining the erythropoietin response." An editorial accompanying their article suggested that the failure of the erythropoietin level to . . .