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A 60-year-old female with a history of hypertension and hyperl ipidemia presen ts in Decem ber for further evaluation of several months history of general ized fatigue. Patien t denies bleeding. weigh t loss, or changes in appetite. Physical exami nation reveals no jaundice. lymphadenopathy, or organomegaly. Laboratory evaluation shows hemoglobi n of 8.7 g/dL, mean corpuscular volume (MCV) of 1 1 0 FL. leukocyte count of 5,600/J.LL, and platelet count of 1 7LJ ,OOO/J.LL. Peripheral blood smear is shown below.
What are the most likely findings on direct antiglobin test?
- Negative for IgG and complement
- Positive for complement only
- Positive for IgG and complement
- Positive for IgG only
Medicine
B. Washing of the RBCs during direct antiglobin test results in dissociation of abnormal antibodies from the surface of RBCs. This leaves only complement attached to the RBC surface. Since the majority of cold agglutinin disease cases are caused by a pathologic IgM, testing for IgG will pro-duce negative results. In the rare case of IgG cold agglutinin disease, poor fixation of abnormal anti-body to the surface of the RBC might result in its dissociation and removal during RBC washing, leaving only complement.
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