Background Information of Polychromasia
Polychromasia is used to describe RBCs in PBF that have their cytoplasm stained shades of greyish blue or purplish (instead of their normal pink/red). These are pre-matured RBCs released from the bone marrow during blood formation. Polychromasia is usually an indication of bone marrow stress as well as immature red blood cells. These young pre-matured RBCs are convieniently called reticulocytes, however, not all reticulocytes are polychromatophilic.
The dark greyish blue/purplish staining observed in polychromatic RBCs is due to the ribosomes still left on the immature blood cells, which are not found on mature red blood cells. The typical life span of a RBC is approximately 120 days and the duration of a reticulocyte found in the blood stream is one day
The percentage of reticulocytes calculated to be in the blood at any given time indicates the rapidity of the red blood cell turnover in a healthy patient. The number of reticulocytes, however, reflects the amount of erythropoiesis that has occurred on any certain day.The absolute number of reticulocytes is referred to as the reticulocyte index and is calculated by adjusting the reticulocyte percentage by the ratio of observed hematocrit to expected hematocrit to get the 'corrected' reticulocyte count.
Polychromatic RBCs as mentioned earlier appear to be more densely stained and have shades of purplish/greyish-blue. Sometimes it might appear distinguishably bigger than normal RBCs.