For inclusion into the study, dogs had to be diagnosed with IMHA based on the presence of regenerative anemia (hematocrit 60,000 reticulocytes/μL), evidence of hemolysis (hyperbilirubinemia, hemoglobinemia, bilirubinuria, or hemoglobinuria), and at least one or more of the following criteria: presence of spontaneous persistent agglutination (that persisted after dilution with saline); at least 2+ spherocytes noted on blood smear; or a positive direct Coombs' test.