The measurement of the total volume of red cells in man: a non-radioactive approach using biotin.

Present methods for measuring red cell volume are based on the dilution of radioactively labelled cells. This precludes the investigation in neonates and pregnant women. We present a simple method for labelling red cells with biotin. These cells may be injected intravenously and subsequently detected using streptavidin-FITC and flow-cytometry. A comparison of the red cell volume estimated using both 51Cr and biotin labelled cells in 19 patients showed no consistent clinically significant difference between the two. This novel label appears to allow red volume to be reliably estimated without using radioactivity.