Good agreement of conventional and gel-based direct agglutination test in immune-mediated haemolytic anaemia

Canine (n = 247) and feline (n = 74) blood samples were submitted for DAT testing to two laboratories. A subset of canine samples was categorized as having idiopathic IMHA, secondary IMHA, or no IMHA.The kappa values for agreement between the tests were in one laboratory 0.86 for canine and 0.58 for feline samples, and in the other 0.48 for canine samples. The lower agreement in the second laboratory was caused by a high number of positive canine DATs for which the gel test was negative. This group included significantly more dogs with secondary IMHA.The gel test might be used as a screening test for idiopathic IMHA and is less often positive in secondary IMHA than the DAT.Immune-mediated haemolytic anaemia (IMHA) is caused by the binding of antibodies to the surface of red blood cells (RBCs). The production of such antibodies can be a primary autoimmune phenomenon or be associated with underlying neoplasia, chronic infections, inflammatory disease or be triggered by exposure to drugs or vaccines (secondary IMHA) [1]. The criteria used to define IMHA in dogs and cats vary between different studies; however, it is generally accepted that a positive direct agglutination test (DAT), marked spherocytosis or true autoagglutination are three hallmarks of canine IMHA. At least one of these changes must be present in a patient with haemolytic anaemia to warrant a diagnosis of IMHA [2].The DAT demonstrates the presence of anti-erythrocyte antibodies by incubating a suspension of washed patient erythrocytes with polyvalent or monovalent antisera specific for immunoglobulin or complement. More recently, a gel-based test has been developed (Diamed, Cressier, Switzerland) [3]. The gel test is fast and easy to perform and has the potential for in-house use. A whole-blood sample may be used (instead of washed and resuspended RBCs) and the test uses a smaller blood volume than that required for the DAT [4].The aims of this study were: (1) to perform a comparison between the feline