7. Kay Elliott, a member of the AABB Standards Committee, has submitted the following response which is quoted verbatim with her permission. (This response may not reflect official AABB policy and has not gone through the peer review process.)

"More on antibody identification in alloimmunized patients. If the trigger for performing a panel is increase in strength in reaction - how will you detect an increase in a serum already reacting 4+? If the trigger is a positive DAT, how can that be a valid test if all of the incompatible donor cells have been destroyed? If the trigger is an incompatible crossmatch, how will that be an effective trigger if the donors are negative for the antigen that reacts with the "new" antibody? If the trigger is observing for clinical signs of hemolysis, then as an assessor I would be looking for instruction in the SOP that requires techs to check bilirubin and Hb & Hct results and to document that check in the patient record. While all of those above may be tests that detect antibody, in alloimmunized patients their use for antibody detection is less than the standard of practice for nonimmunized patients. I see a contradiction in practice between alloimmunized patients and nonimmunized patients. That is, for the initial screen all facilities use either a 2 or 3 cell screen with all antigens to commonly seen antibodies represented on those cells - some with double dose antigen expression. But for alloimmunized patients ( those who we know are good responders) the same practice is not used once they have been transfused after the initial workup. In fact, one facility response states that they wait until the patient has a delayed reaction before identifying the antibody and providing antigen-negative blood. It would seem that it would be in the best interest of the patient to identify that antibody prior to transfusion. Thus the intent of Standard 5.12.3.3 (response #4, above). Further support for this opinion can be found in the AABB Publication Questions and Answers, 6th and 7th ED. "

ADDENDA May 9, 2002

8. In response to reply #7 from a member of the AABB Standards Committee, the following rebuttal has been suggested by a blood banker in Michigan:

"First, a DAT is not a required part of pretransfusion testing, and there are substantive data showing the poor predictive value of this test in detecting an alloimmune response to previous recent transfusion that is not evident from the antibody screen. Second, I do not believe it is mandated that antibody screen has to be done. I could be wrong, but the screen was initially introduced so that we could manage our blood inventory, which then led to the development of protocols such as MSBOS. Standards and the FDA tell us how to do a screen, but there is no reason why we can't simply do an antiglobulin crossmatch for all units transfused without doing an antibody screen. Third, if units lacking antigens reactive with known antibodies are incompatible, what would cause that reactivity if not another antibody? Yes, the unit could have a positive DAT but that is uncommon. Fourth, if another antibody is present, does it matter that the crossmatched units lack that antigen? They can be transfused without untoward effect. Fifth, there is a notion that patients who have already made one antibody are more likely to make additional antibodies than a nonalloimmunized patient will make their first antibody. Where are the data? Finally, all of our patients are best served if we utilize our resources wisely. No doubt some would benefit if we were doing routine pretransfusion DATs, antiglobulin crossmatches on all units transfused, and a 3-cell-sample screening set to provide double-dose antigen expression on a routine basis. However, many of us no longer have those resources, and must focus on what is truly important. Making sure that blood of the correct ABO type is given to the right patient is of paramount importance."

9. In reply to response #1 from Texas, a California blood banker reports that her hospital transfusion service SOP requires that an investigation for new antibodies be performed every 3 days. All patients with known antibodies have a DAT done with their IgG crossmatches and pretransfusion workup. A select panel is performed which includes at least one cell positive for the known antibody(s) (to show how it is reacting or if it is still reacting) and the rest of the panel cells are to be negative for the known antibody (s). She reports having seen patients with prolonged hospital stays develop new antibodies while being continuously transfused. If this method had not been employed a delayed transfusion reaction may have occurred. Typically these antibodies have been Duffy. She adds that she would be very concerned as a patient if she needed transfusions and discovered that new antibodies were only being looked for every 90 days!

Editor's note: In fairness to the Texas report in #1, that blood banker did say that 'If the reaction strength is stronger or if there is a reaction with a screening cell that contains antigens different from the one reacting with the previously identified antibody, then a panel is repeated.'

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Ira A. Shulman, MD
CBBS e-Network Forum Editor & Moderator