Analysis of Red Cell Mass and Plasma Volume in Patients With Polycythemia

Abstract Context.—Polycythemia describes an increased proportion of red blood cells in the peripheral blood. In absolute polycythemia, there is increased red cell mass (RCM) with normal plasma volume, in contrast with apparent polycythemia, in which there is increased or normal RCM and decreased plasma volume. In order to deliver the appropriate treatment it is necessary to differentiate between the two. Objective.—A retrospective analysis of RCM and plasma volume data are presented, with special attention to different methods of RCM interpretation. Design.—The measurements of RCM and plasma volume in 64 patients were compared with the venous and whole-body packed cell volume, and the incidence of absolute and apparent polycythemia was determined for increasing hematocrit levels. Measurements of RCM and plasma volume were performed using chromium 51–labeled red cells and iodine 125–labeled albumin, respectively. The measured RCM of each patient was expressed as a percentage of the mean expected RCM and wa...