We had an incident occur as follows: Two specimens were collected by nursing and properly labeled by nursing using labels provided by registration (contains all pertinent pt identification information and then some). Both specimens come to the transfusion service. Orders are located in the lab computer system, received and labels printed. While attaching the lab labels to the specimen the tech is interrupted (multiple times) and in the course fo labeling switches labels with tubes so that label A is attached to specimen B and vice-a-versa. Even though the tech who labeled the tube left the name and id number from the original label exposed the error was not caught by the other tech performing testing that shift. Consequently one of the pt's received an ABO incompatible unit of blood (it was caught and stopped after 100cc infused). Pt survived. FDA notified etc. We are now at the point of coming up with a way to keep this from happening again. We have a policy in place that states that at the time a new label is being attached that both the patient name and id number on BOTH labels MUST be MATCHED, then the label may be attached to the tube. However, our supervisor feels that the FDA will want us to come up with something new to prevent this from happening. By the way this is the first time I can remember this happening in our labs and I've been here for over 20 years. Does anyone have any other policy, procedure or method they use when putting a new label on an already labeled specimen? Sorry this is so long and thanks in advance for any ideas, help.