Direct immunofluorescent assay for isotype specific antibodies coating erythrocytes in dogs and horses with immune mediated anemia
The Direct Immunofluorescent assay detects antibodies on red blood cells. For dogs, we use fluorescent labeled polyclonal antisera to canine IgG, IgM, IgA, and C3. For horses, we use fluorescent labeled polyclonal antisera to equine IgG, IgM and IgA. This test is more sensitive that the Coomb’s anti-globulin agglutination test, because it is not affected by the prozone effect. The prozone effect is when the agglutination based Coomb’s test is negative at low dilutions of Coomb’s reagent. The sensitivity is 100% and the specificity of the direct immunofluorescent assay is 87.5% determined by population of dogs with immune mediated hemolytic anemia (J. Vet. Intern. Med. 2000, 14:190-196). The test does not differentiate primary (idiopathic or autoimmune) immune mediated hemolytic anemia (IMHA) from secondary causes for IMHA. We have identified antibodies on the surface of equine red cells in cases of penicillin induced IMHA, clostridial myositis, and neonatal isoerythrolysis.