Recently, I typed a patient as A who had a history of O. I asked for a new sample and the new sample typed as A. I then suspected that the "O" sample had been incorrectly collected. I discussed this w/ my super who had another theory. She said that there are times that a patient can change ABO type. i.e. if the patient is septic, the bacteria can de-nature the antigens on the surface of the RBC causing the reactions that don't reflect the patients true ABO. I would think that if that were the case the back type would reflect the patient's "true" ABO. How septic does one have to be to affect the front type? Any comments?