Was the patient recently transfused? We had a situation several years ago where the patient sample results were one type on the Vision and another type in tube. I learned that the instrument samples red cells from the bottom of the patient specimen which, after centrifugation, is where the majority of the more dense transfused cells are vs. the top of the red cell layer where the less dense autologous red cells are. This cause for a forward typing discrepancy was confirmed after communications with Ortho.
The theory was confirmed with manual gel testing where red cells were sampled from the top, middle and bottom of the red cell layer of the patient's specimen. The top layer of red cells were Group O, the middle and bottom were primarily Group A. This patient was discovered to be Group O after receiving several Group A RBC transfusions. The reverse typing showed reactivity only with Group B red cells at that time.
