Measurement of red cell survival using biotin-labeled red cells: validation against Cr-51-labeled red cells

BACKGROUND: Anemia is a serious problem in the fetus and preterm infant. To investigate the physiology and pathophysiology of anemia and to assess res ponses to blood transfusions and erythropoietin therapy, measurement of cir culating red cell survival would be useful. STUDY DESIGN AND METHODS: Because the standard Cr-51 method exposes the pat ient or subject to radiation, a practical, accurate method for measuring re d cell survival was developed on the basis of determining the number of bio tin-labeled red cells that persist in the circulation by using fluorescein- labeled avidin and flow cytometry. In addition, disappearance of total biot in label was measured by using I-125-streptavidin. Results of each detectio n method were compared to red cell survival measured by the standard Cr-51 method. RESULTS: Biotinylated cells persisted in circulation with life spans approa ching normal. Despite near-normal persistence in circulation of the biotin- labeled cells, about one-half of the biotin label left the circulation over the first few weeks, causing early curvilinear disappearance. This observa tion is consistent with the hypothesis that about one-half of the biotin la bel leaves the red cells. However, about one-half of the biotin was permane ntly attached, which produced linear disappearance and approximately normal life span estimates for the linear survival curve appearing after the firs t few weeks. CONCLUSION: Red cell survival can be measured accurately in humans using en umeration of biotinylated red cells. The method is practical and does not e xpose the patient to radiation.