Estimation of red cell mass and plasma volume in patients with polycythemia vera using chromium

Objectives The red cell mass (RCM) is usually determined by radioisotope labeling of red blood cells according to the recommendations of the International committee for Standardization in Haematology. To retrospectively analyze the RCM and plasma volume, determined by ⁵¹Chromium labeled erythrocytes method

Methods Study was performed on 57 patients, using ⁵¹Chromium (1.5-3.5 kBq) labelled erythrocytes. Radioactivity in the standard and plasma was measured using a calibrated gamma counter. The results were expressed in the traditional units of mL/kgbwt. The final diagnosis of polycythemia was made on the basis of increased RCM, palpable splenomegaly and bone marrow histology. The normal RCM and plasma volume values were committed to be 25 mL/kgbwt (F), 30 mL/kgbwt (M) and 39 mL/kgbwt (F) and 40 mL/kgbwt (M), respectively.

Results The measurements of RCM and plasma volume in 45 men and 12 women (mean age: 46.23 ± 15.36 yrs, mean bwt 59.70 kg and mean Hb 17.57) were compared. 43 patients (9F and 34M) among them had increased RCM (mean 43.68 mL/kgbwt). 10 patients (2F and 8M) had absolute polycythemia with increased RCM and plasma volume within normal limits. 33 patients (7F and 26M) had apparent polycythemia while 12 patients (1F & 11M) had relative polycythemia.

Conclusions The blood volume studies are useful in patients with an increased hematocrit and no other biological/clinical symptoms suggesting polycythemia. Direct RCM measurement is a more accurate indicator of the body’s red cell content.