Reticulocyte-based estimation of red blood cell lifespan

We introduce a new, minimally invasive laboratory technique called reticulocyte-based estimation of lifespan (REBEL) of erythrocytes in humans. Its major advantage over existing techniques is its applicability to patients with both changing and steady-state erythropoiesis status. The feasibility of REBEL was tested in five patients with hemodialysis-dependent end-stage renal disease. The RNA degradation half-life was first determined for each subject on day 1 by flow cytometry measurement of the decay rate of thiazole orange stain. Reticulocyte age distribution was then measured from residual RNA content weekly for 2 months to estimate the RBC production rate time course. Mean RBC lifespan per subject was estimated by fitting the integrated RBC production rate over time to the measured RBC count and optimizing the integration limits. The mean reticulocyte RNA half-life was 0.71±0.11 days. The small coefficient of variation (15.6%) indicated that the degradation rate of RNA did not vary substantially between subjects. The mean RBC lifespan (T_RBC=76.6±23.8 days) was comparable to the reported values for this patient population.