Measurement of red-cell and plasma volumes

The different methods of measurement of red blood cell and plasma volumes are exposed. The "Gold Standard" remains the measurement of whole blood volume with 51 chromium labelled red cells and the calculation of red blood cell and plasma volumes with the result of microhematocrit. In some cases, the direct measurement of plasma volume is performed with 125 I-human serum albumin. The mode of expression of the experimental results of blood volume is discussed. Two main modes are employed: expression as a function of the body weight (ml/kg) or as a percent of the value of a normal subject (same age and body area). The usefulness of measurement of red cell and plasma volumes in the diagnosis of true and apparent polycythemia is discussed.