WHAT IS COOMBS’ TEST (DIRECT ANTIGLOBULIN TEST)?
The direct Coombs’ test involves adding Coombs’ antihuman globulin serum to a client’s washed red blood cells and observing for agglutination, which signals the presence of previously undetected IgG antibodies, complement, or immunoglobulins on the surfaces of the client’s erythrocytes. The Coombs’ antiglobulin contains antibodies to IgG and several complement components. The antibodies detected by the direct Coombs’ test are difficult to detect any other way because they are left over from incomplete antigen-antibody reactions and, though present on the erythrocyte surfaces remains invisible. The Coombs’ antiglobulin causes completion of the antigen-antibody reaction, thus making the antibodies identifiable as they begin clumping.