Red cell-bound immunoglobulins and complement measured by an enzyme-linked antiglobulin test in dogs with autoimmune haemolysis or other anaemias.

A direct enzyme-linked antiglobulin test (DELAT) was used to measure IgG, IgM, IgA and C3 bound to the red blood cells (RBC) of anaemic dogs. One or more of these parameters was raised in 78 per cent of the cases tested, and elevated levels of bound IgG, IgM, IgA and C3 was the most common pattern recorded. When the DELAT-positive animals were divided into two groups on the basis of clinical findings, the two categories differed serologically. Cases diagnosed clinically as primary autoimmune haemolytic anaemia (AIHA) were typified by the demonstration of specific antibody binding to RBC, had significantly higher levels of RBC-bound IgG (P < 0.001) and IgM (P < 0.02) and included a significantly (P < 0.01) higher proportion of the dogs with at least three DELAT parameters raised. The second group comprised the DELAT-positive dogs with other diseases. In most of these cases, RBC-specific antibody was not detectable and there was a significant (rs = 0.62, P < 0.001) relationship between RBC-bound and serum IgG levels, suggesting that the immunoglobulin was reacting with the RBC non-specifically in a concentration-dependent manner. It is concluded that elevated levels of RBC-bound immunoglobulin and, or, complement are detectable with the DELAT in most anaemic dogs, but that this finding is not necessarily associated with autoimmune haemolysis.