Should whole-body red cell mass be measured or calculated?
Balga I; Solenthaler M; Furlan M Central Hematology Laboratory, University Hospital, Inselspital, Bern, Switzerland. The whole-body volume of red blood cells must be known for correct diagnosis of polycythemia vera. Since the venous hematocrit may not correctly reflect the absolute amount of red blood cells, the red cell mass (RCM) is usually determined by radioisotope labeling of red blood cells according to recommendations of the International Committee for Standardization in Haematology. We examined whether the radioisotope labeling procedure can be replaced by a simple calculation of RCM from the values of venous blood hematocrit and plasma volume, using an empirical factor (Ratio f) equal to the mean ratio between whole-body and venous hematocrit. A retrospective study was performed of 264 cases in which the RCM was assayed using (51)Cr or (99m)Tc for red cell labeling, and (125)I-labeled albumin was used for estimation of plasma volume. The results showed wide scattering of Ratio
