A method for the continuous calculation of the age of labeled red blood cells

New methods for labeling red blood cells (RBC) and monitoring their survival have made it possible to explore changes in the properties of RBC as they age in the circulation. We have adapted a method, originally developed for studying wild animals, to calculate the age of a random sample of labeled RBC from their survival curve. We also show how this method can be expanded to allow continuous calculation of the mean age of the labeled RBC population at any time after labeling. It is expected that this analytical approach will be useful in the study of age-dependent RBC changes.