Feline Erythrocytic Osmotic Fragility in Normal and Anemic Cats—A Preliminary Study

Erythrocyte osmotic fragility is an excellent parameter for evaluating the red blood cell (RBC) membrane, which may be abnormal in several pathological conditions. The flow cytometer is a powerful tool that analyzes a single cell in a solution and can detect alterations in RBCs, providing key differential diagnostic information. Both the osmotic fragility test (OFT) and flow cytometry are valuable diagnostic tools in veterinary medicine, but their diagnostic usefulness in anemic cats has not yet been determined. This study aimed to evaluate RBC membrane strength using an OFT in non-anemic and anemic cats and to compare RBC size and density using a flow cytometer in non-anemic and anemic cats. A total of 18 cats in the non-anemic group and 18 cats in the anemic group, divided into adults and seniors, were included in this study. Blood samples were collected for a complete blood count (CBC) and blood chemistry. The remaining blood was used for OFT to evaluate 50% hemolysis from the hemolysis curve and for the flow cytometer to measure forward scatter characteristics (FSC) and side scatter characteristics (SSC). The result of OFT showed no significant difference in OF between normal and anemic cats in the adult and senior groups. In terms of flow cytometry analysis, normal and anemic cats in the adult group showed no significant difference in the FSC (p = 0.769). On the other hand, the FSCs of normal senior cats were significantly higher than those of anemic cats (p = 0.0486). The SSCs of normal cats were significantly higher than those of anemic cats in the adult group (p = 0.048). However, the SSCs of the senior group showed no significant difference (p = 0.074). Based on these results, we concluded that, in the senior group, normal cats had higher FSCs than anemic cats, and in the adult group, normal cats had higher SSCs than anemic cats. However, both normal and anemic cats exhibited similar osmotic fragility. Further studies on various diseases are suggested.