Erythrocyte-bound immunoglobulin isotypes in dogs with immune-mediated hemolytic anemia: 54 cases (2001-2010)

Objective-To identify erythrocyte-bound immunoglobulin (Ig) isotypes in dogs with primary immune-mediated hemolytic anemia (IMHA). Design-Retrospective case series. Animals-54 dogs with IMHA. Procedures-Medical records of dogs with IMHA diagnosed between January 2001 and April 2010 were examined. Immunoglobulin isotype (tested via direct immunofluorescence by flow cytometry to identify erythrocyte-bound Ig), Hct, serum bilirubin concentration, presence of autoagglutination, degree of spherocytosis, duration of hospitalization, and 90-day outcome were recorded. Results-The Hct on admission was significantly lower in dogs with IgG and IgM isotypes bound to erythrocytes, compared with dogs with a single Ig isotype, and the degree of spherocytosis was greater in dogs with IgG and IgM bound to erythrocytes, compared with dogs that only had IgM. Dogs with only IgM were not more likely to have autoagglutination, compared with dogs that only had IgG on the erythrocyte surface. Although Ig isotype was not associated with survival time, initial serum total bilirubin concentration was higher in nonsurvivors. Conclusions and Clinical Relevance-Results suggested that dogs with IMHA with ≥ 2 Ig isotypes bound to erythrocytes, particularly IgG and IgM, are likely to have a more severe degree of anemia, spherocytosis, and autoagglutination.