Erythrocyte creatine in cord blood

Erythrocyte creatine (EC) content and reticulocyte counts were compared in normal adults, pediatric patients with hemolytic anemia, and cord blood. A good correlation between reticulocyte count and EC content was found in normal subjects and patients with hemolysis, thus confirming the usefulness of creatine as an estimate of mean red cell age in these populations. No significant correlation (p greater than 0.1) was observed between the two measurements in cord blood. While reticulocyte counts were significantly elevated (p less than 0.001) in cord blood when compared to normal adults (indicating the presence of a young mean red cell age), EC concentrations in most samples were not correspondingly high. These results may indicate that creatine is not well synthesized by the neonatal red blood cell.