Multiple red cell volumes (RCV) can be determined simultaneously and independently in humans in vivo using red cells (RBCs) labeled at 4 biotin densities

Abstract

Anemia is a common and serious problem in critically ill neonates. To investigate the pathophysiology of anemia and to assess responses to red blood cell (RBC) transfusions and erythropoietin therapy, repeated measurement of RCV and blood volume would be useful. We previously reported the in vivo validation of a nonradioactive method for determination of RCV in adults using flow cytometric enumeration of RBCs labeled at one or two biotin densities. Here we report the simultaneous measurement of RCV in 2 adult subjects using 4 populations of RBCs labeled at distinct biotin densities. In one subject, biotinylation reagent concentrations from 9 to 243 μg/mL of RBC produced a mean RCV of 24 ± 0.6 mL/kg; CV= 3%. In the second subject, biotinylation reagent concentrations from 6 to 192 μg/mL of RBC produced a mean RCV of 29 ± 0.8 mL/kg; CV= 3%. RCV values were not different by ANOVA among the 4 densities for either subject. These studies provide evidence that RBCs biotinylated at discrete densities can be used for simultaneous and repeated independent measurements of RCV in vivo in humans. Because only small sample volumes are required and because the subject is not exposed to radiation, we speculate that this RCV method will be useful in investigating the physiology and pathophysiology of anemia in pregnant women, fetuses, and infants. NIH P01 HL046925; Thrasher Research Foundation 02825‐3.