The Sysmex XN-1000V analyzer can identify those reticulocytes with high RNA content and fluorescence, providing the immature reticulocyte fraction (IRF). While this parameter has been used in human medicine to identify the cause of anemia, few studies have focused on its use in veterinary medicine. In this study, we determined the IRF and related reticulocyte parameters in a large population of non-anemic and anemic dogs and cats (subclassified depending on the origin of their anemia). The IRF was significantly higher in hemolytic anemias compared to hemorrhagic ones in both species. Moreover, the IRF was significantly lower in dogs and cats with bone marrow failure than in other non-regenerative anemias and in both groups compared to pre-regenerative anemias. The accurate cut-off values for the differential in regenerative anemias and reference ranges for both species using the Sysmex XN-1000V are also reported. The measurement of the IRF in this analyzer can help clinicians to further classify the type of anemia in both species.
Keywords: anemia; cats; dogs; hematology; immature reticulocyte fraction; reticulocytes.