Serum erythropoietin titres in the anaemia of premature infants.

Erythropoietin (EPO) titres in the serum of premature infants were determined by an in vitro method using radioiron incorporation into haem in fetal mouse liver cells in culture. The serum EPO titres in 12 premature infants at birth were significantly lower than those of normal adults. In those premature infants who developed anaemia the serum EPO titres increased significantly by 4-6 weeks after birth, confirming that EPO production increases in premature infants in early days of life.