Background and Objectives: A patient experienced a severe haemolytic transfusion reaction. Neither the haemolytic property nor the specificity of the causative antibody had been sufficiently recognised when performing a microcolumn gel test. Materials and Methods: Subsequent to the transfusion reaction, the serological property and specificity of the causative antibody were analysed. Tube and gel test methods were compared, as were various reagent red cell specimens and their constituents. Results: A haemolytic anti-Vel was detected in the tube test. In contrast, the particular commercial gel test kit used did not reveal the haemolytic property or specificity of the antibody. Our experiments suggest that this was apparently due to the presence of EDTA in the low ionic strength saline solution of the test kit. Conclusion: In rare cases life-threatening haemolytic activity of an irregular blood group antibody may be undetected by a commercial microcolumn gel test kit in which EDTA is a constituent.