Mean corpuscular volume is not a reliable marker of red cell age in case of anisocytosis.

The present study was designed to determine the effect of anisocytosis on the association of MCV values with HbA1c and reticulocyte counts as markers of red cell age. Normo-, micro- and macrocytic samples, fractionated by counterflow centrifugal elutriation were studied. The previously described correlation between MCV and HbA1c was only observed in normal samples and in the middle fractions of samples with anisocytosis. At both extremes of the elutriation profile, curves for HbA1c content and reticulocyte count levelled out. Furthermore, in fractions containing the largest red cells of the microcytic series and the smallest red cells of normo- and macrocytic samples, reticulocyte count decreased while HbA1c content increased with increasing MCV. From these data it is concluded that MCV is not an absolute determinant of red cell age in case of anisocytosis.