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• Significance of the Pattern of Positive Direct Antiglobulin (Coombs') Test in the Diagnosis of Autoimmune Hemolytic Anemia (AIHA)

• Anti-IgG Anti-C3 Antigen Occurrence Comment

• + - Rh protein Drugs: penicillin, Warm AIHA, IgG

• aldomet; not in SLE

• + + Glycoprotein Less common AIHA Ab is IgG which fixes complement

• - + Polysaccharide Cold Agglutinin Ab is IgM

• - + P blood group Paroxysmal Cold Donath Landsteiner Hemoglobinuria Ab is IgG*

• ± ± Protein Drug-related: Hapten Drug needed to detect antibody Ab is IgG or IgM

• * The Donath-Landsteiner IgG antibody attaches to the red cell in the cold, fixing and activating complement. When the cells are warmed, complement remains attached, but the IgG antibody dissociates from the red cell.