Erythrocyte anisocytosis. Visual inspection of blood films vs automated analysis of red blood cell distribution width.

An improved anemia classification may be available by combining measures of red blood cell size variability with mean corpuscular volume. Visual inspection of the peripheral blood film allows semiquantitative description of anisocytosis while quantitative measures are determined from electronic cell counter analyzers' red blood cell distribution width. We evaluated correlations between semiquantitative and quantitative measures of anisocytosis for different groups of observers. Hematologists', medical students', and medical residents' semiquantitative assessment of anisocytosis correlated with the quantitative red blood cell distribution width. The interobserver variability demonstrated that all observers correlated with each other, while the intraobserver variability of semiquantitative anisocytosis demonstrated that observers were more precise than could be predicted by chance. However, the extreme precision of the red blood cell distribution width strongly suggests that it should be the "gold standard" for measuring red blood cell size variability.