Autoantibodies are immunoglobulins directed against self-antigens. Most autoantibodies react with high-incidence red cell antigens. Recognition of these antibodies is important during serologic testing.
Autoantibodies may complicate routine testing by causing ABO and Rh typing problems.
AIHA is usually confirmed by a positive direct antiglobulin test (DAT) and demonstration of the autoantibody in the plasma or eluate.
AIHA is classified as either cold-reactive or warm-reactive. Table 1 lists different types of AIHA and the antibody classes involved. These will be discussed in detail on the following pages.
Table 1. Types of Autoimmune Hemolytic Anemia.| Autoimmune Hemolytic Anemia | Antibody Type | Complement Association |
| Warm Autoimmune Hemolytic Anemia (WAIHA) | IgG autoantibodies | Sometimes |
| Cold Agglutinin Syndrome (CAS) | IgM autoantibodies | Yes |
| Mixed-Type (serological features of both warm and cold autoantibodies) | Both IgM and IgG autoantibodies
| Yes |
| Paroxysmal Cold Hemoglobinuria (PCH) | IgG biphasic hemolysin | Yes |
