Simplified, anemia can be classified by morphology, specifically the mean cell volume.
- Microcytic: MCV <80.0 fL
- Normocytic: 80.0-100.0 fL
- Macrocytic: >100.0 fL
In the most general of terms, microcytic anemia will also be hypochromic (MCHC <32.0%), indicating a lower hemoglobin concentration per cell.
In addition, the RDW, or red cell distribution width, is most helpful in determining the variation in red blood cell size. Rodak's text identified the reference range for the RDW as 11.5-14.5 %.6 Higher than 14.5 % would indicate a greater than normal variation in red blood cell size and this must be considered in conjunction with the MCV and confirmed regarding the populations present. A normal MCV with a high RDW represents more than one size population with microcytes, macrocytes, or both present.
6. Keohane, E. M., Otto, C.N., Walenga, J. M. (2019). Rodak's Hematology Clinical Principles and Applications. St. Louis., Elsevier, 6th Edition.
