Demographic Characteristics, Survival and Prognostic Factors for Mortality in Cats with Primary Immune‐Mediated Hemolytic Anemia

BACKGROUND: Immune‐mediated hemolytic anemia (IMHA) is uncommon in cats, but may result in severe disease. Demographic predispositions for development of the disease and prognostic factors for mortality have not been investigated previously. HYPOTHESIS/OBJECTIVES: To explore possible demographic predispositions for development of primary IMHA in cats and to investigate possible prognostic factors for mortality. ANIMALS: 107 client‐owned cats with IMHA, of which 72 had primary IMHA and 35 had secondary IMHA, and 9,194 control cats. METHODS: Data were collected retrospectively from records of cats with IMHA, defined by the presence of anemia and concurrent autoagglutination, ghost cells without oxidative damage on fresh blood smear, positive titer in a direct antiglobulin test, or evidence of phagocytosis of erythroid precursors in bone marrow. Odds ratios were calculated to assess the risk of development of primary IMHA in different demographic groups and Cox proportional hazards analysis was conducted to evaluate prognostic factors. RESULTS: No sex or breed predisposition was identified for the development of primary IMHA in comparison to the control cats, but cats in the age range 2.1–5.9 years were predisposed. Higher total bilirubin concentration and age were significant negative prognostic factors and higher lymphocyte numbers and serum globulin concentration were positive prognostic factors in a multivariable model. CONCLUSIONS AND CLINICAL IMPORTANCE: Young adult cats were more likely to develop primary IMHA than other groups, but no apparent male predisposition was identified in this study, contrary to previous reports. Several prognostic factors were identified, which may be helpful in guiding clinical practice in the future.