The red cell mass, plasma erythropoietin and spleen size in apparent polycythaemia

It has been shown previously that measurement of the spleen size and plasma erythropoietin (EPO) concentration are valuable adjuncts in the diagnostic work-up of patients with polycythaemia vera. The aim of the present work w as to evaluate their value in the assessment of apparent polycythaemia (AP) . Therefore, over a 24-month period we routinely performed bone marrow biop sies, measurement of red cell mass (RCM) and plasma volume (PV), spleen siz e determination by gamma camera scintigraphy and determination of the plasm a EPO concentration in consecutive patients referred to us because of eleva ted values for packed cell volume (>0.48 in females and >0.51 in males). Af ter having excluded patients with clonal and secondary polycythaemias we we re left with 38 patients (27 males and II females) with AP. In all of them the measured RCM was within normal range, i.e. <36 ml/kg for males and < 32 ml/kg for females. The subjects were characterized by moderate increase in RCM and a concomitant moderate decrease in PV. Thus, as an average the mea sured RCM exceeded the predicted values by 14% in males and by 12% in femal es; conversely, as compared to the predicted values the average measured va lue for PV was reduced by 17% in males and by 8% in females. The average RC M for males was 29+/-3 ml/kg; the corresponding figure for females was 23+/ -14 ml/kg. It was shown that 86% of the subjects had plasma EPO concentrati ons within the control range; the remaining had values slightly above or be low the control range. The mean posterior spleen scan area was 57+/-16 cm(2 ) and mean left lateral area 57+/-17 cm(2): the reference value for spleen scan area (for both projections) is 57+/-12 cm(2). Of the patients 35/38 (9 2%) had a spleen scan area within the mean+2SD for controls and 38 subjects (100%) had values within the mean+3SD. It is concluded that measurement of plasma EPO and a careful assessment of the spleen size should always be co nsidered in the evaluation of patients with elevated values for venous pack ed cell volume.