Regenerative anemia identification in cats: Red blood cell indices or morphology, what to use?

Background and Aim: Anemia, a clinical condition characterized by reduced erythrocytes, is often observed in cats. Regeneration indicates that the bone marrow can respond appropriately to anemia. The absolute reticulocyte count is the reference for differentiating regenerative and non-regenerative anemia, while red blood cell (RBC) indices and morphology provide supplementary information. This study aimed to identify anemia types and establish the most reliable RBC indices and morphology methods in agreement with the reference method. Materials and Methods: One hundred forty-five cases of cat anemia were prospectively classified using two methods: RBC indices and RBC morphology, and subsequently compared with the absolute reticulocyte count. Results: Based on RBC indices assessment, 27 cases (19%) exhibited regenerative anemia. Based on RBC morphology, 29 (20%) cases were identified as having regenerative anemia. Using the reticulocyte absolute count as a reference method, 34 (23.4%) cases of regenerative anemia were identified. The findings indicated that RBC indices and RBC morphology did not align in evaluating medullary regeneration and that there is a good degree of agreement between RBC morphology assessment and the reticulocyte absolute count in identifying regenerative anemias. Conclusion: Blood smear analysis of RBC morphology was more dependable for classifying regenerative anemia than RBC indices. Further studies should be conducted with a larger number of animals and that allow the identification of the cause of anemia and the monitoring of the animal. Keywords: anemia, cats, red blood cell indices, red blood cell morphology, reticulocyte.