Interpretation of measured red cell mass and plasma volume in males with elevated venous PCV values

Abstract

A method of interpretation of red cell mass (RCM) and plasma volume (PV) data is described. The results in 188 males with PCV [packed cell volume] over 0.50 places the patients in 4 groups: true (absolute) polycythemias, relative (low plasma volume) polycythemias, high normal red cell mass (HNRCM) and physiological variant. Absolute polycythemias were increasingly frequent at higher PCV levels but only reached 100% at a PCV of 0.60. They showed an 18% incidence in the lower PCV range of 0.500-0.519. Relative (low PV) polycythemia was found in 18% of the patients with PCV values in the range 0.500 to 0.599. Although the HNRCM and physiological variant types found mainly in the lower PCV ranges they occurred at the 0.54 level. While this method of interpretation of RCM and PV data is perhaps arbitrary, it does provide a basis for the proper study of the common group of patients with raised PCV levels in which classification, course and treatment are uncertain. Both RCM and PV apparently should be measued at all levels of PCV over 0.50; that relative (low PV) polycythemia is a real entity but less common than sometimes believed; that diuretics do not have a notable part in its causation and that the common HNRCM, physiological variant groups are incompletely understood and require further study.