Abstract
Objective: One of the more neglected procedures in nuclear medicine is the radioisotopic determination of red cell mass (RCM) which is a valuable, cost-effective and easily performed procedure that helps establish the diagnosis of true polycythemia and distinguish it from relative erythrocytosis. Early diagnosis of polycythemia is important since a delay in treatment may be associated with serious complications.
Methods: Whole blood (15–25 ml) was withdrawn and added to a small volume of ACD solution. Chromate-51 (1.48–1.85 MBq) was added to the blood with continuous mixing at 37°–39°C. After incubation, ascorbic acid (50–100 mg) was added to reduce the 51Cr to the trivalent state and stop it from binding to the red cells. The blood was reinjected into the patient and a whole-blood sample was drawn from a different vein at 45 min postinjection. The aliquots from the sample were washed three times in saline and then counted.
Results: If the RCM exceeds the predicted mean normal value by more than 12.5%, the patient is thought to have a high-normal RCM, which may be a physiologic variable, transient anomoly or an early stage of an absolute polycythemia.
Conclusions: Although many labaratories express the results of RCM in terms of ml/kg body weight, this approach may be inaccurate for the individual patient. Based on the literature, a more accurate and practical method of predicting and interpreting RCM is presented.
Footnotes
↵* Current address: Dept. of Nuclear Medicine, Mt. Sinai Medical Center, New York, NY.