The role of carboxylic acids in EDTA-dependent panagglutination

The investigation of a patient blood sample showing a discrepancy between cell grouping and serum confirmation demonstrated a serum agglutinin which reacted with all red blood cells tested when exposed to EDTA. This reaction was 4+ macroscopic at room temperature, 2+ macroscopic with hemolysis at 37 degrees C in albumin, and 1+ macroscopic in the anti-human globulin phase. Agglutination was abolished following dithiothreitol treatment of the patient's serum or following saline washing of the EDTA-exposed test cells. The agglutination reaction was not limited to EDTA, but could be produced with polycarboxylic acids (citrate, L-tartrate, succinate) and monocarboxylic acids (acetate, lactate, propionate, valerate, butyrate). Non-carboxylic acids and low molecular weight ketones or alcohols failed in the agglutination reaction. This study reports an additional example of an IgM "EDTA dependent agglutinin" and demonstrates the dependence on carboxyl groups for its agglutinating activity.