Red blood cell distribution width (RDW)—a mechanism for normal variation and changes in pathological states

Abstract

Background: The red blood cell distribution width (RDW) is a numerical measure of anisocytosis in red blood cells (RBC) which varies with the age and with many diseases and their severity. There has been no satisfactory explanation for these phenomena. Methods: We have used a simple model based on the RBC volumes on entry into and exit from the circulation and the rate of volume loss while in the circulation to predict the mean cell volume (MCV), RDW and lifespan of RBC. Results: When these values were fixed, the model correctly predicted these output values, but the graph for the volume distribution of the RBC and for the lifespan did not match experimental results. When we introduced random variation into each of the input factors, the MCV, RDW and lifespan hardly changed, but the graphs for volume distribution and lifespan matched published results. Conclusions: By varying the coefficient of variation, we could model known changes in the RDW associated with anaemias, diseases the lifespan. The width of the distribution curve (and the coefficient of variation) around a mean value is a measure of the RDW and randomness, and it also reflects the tightness of control of anabolic and catabolic processes. More biological control gives less randomness, a lower RDW and a smaller distribution range, but consumes more metabolic energy. We postulate that the RDW measures the efficiency of biological control and therefore a measure of the functional well-being of the organism.