Hematologists often rely on the results of a positive direct antiglobulin test to confirm a diagnosis of autoimmune hemolytic anemia, but immune hemolytic anemia can occur when no immunoglobulin is detectable by routine methods. Negative DATs in these patients may be due to a small quantity of IgG on their red blood cells (RBCs) (below detectable levels), or when low-affinity anti-IgG is present, or when the autoantibodies are IgA or IgM in nature. A panel of tests developed to detect immunoglobulins on these patients' RBCs may be performed in a few specialized laboratories. These tests can be helpful in instances whereby the clinical picture of AIHA seems obvious, but the laboratory values are misleading.
Keywords: AIHA; Autoimmune hemolytic anemia; Coombs-negative; DAT; DAT-Negative; Low-affinity antibody; Super Coombs.
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