A polychromatophilic cell is a red cell that is slightly larger than a mature red cell whose cytoplasm has a bluish tinge when observed on a normally stained peripheral smear. Most if not all of these cells correspond to reticulocytes, which are RNA containing red cells that are detected either with intravital stains (where blood is not fixed, but rather incubated alive with stain) or FACS analysis using an RNA fluorochrome. Reticulocyte staining is more sensitive than Wright-Giemsa staining for detecting reticulocytes: all true polychromatic cells are reticulocytes, whereas not all reticulocytes would be detectable as polychromatic cells.
