RDW & RBC Histogram — All that Physicians should Know & Apply in Clinical Practice

Traditionally, anemias have been classified on the basis of blood indices (MCV, MCH, and MCHC) and reticulocyte count (reticulocyte production index-RPI). This traditional classification has enjoyed long innings with pathologists and hematologists. Newer automated blood cell analyzers provide an index of red cell volume distribution width (RDW) or heterogeneity and a histogram display of red cell volume distribution. This write-up on classification of anemias based on mean corpuscular volume (MCV) and heterogeneity (RDW) will help clinicians in the initial classification of anemias based on the print-out of automated counters. Also, this new classification obviates the use of reticulocyte count in the initial categorization of anemias. Understanding of RDW & RBC histogram is useful not only in diagnosing early deficiency states when RBC indices are normal but also, in following these patients after treatment, whether the response is physiological or pathological.