A 'fellow' in a transfusion medicine fellowship training program in the Southern USA reports that a recent audit of 'isoagglutinin titer' orders for patients receiving ABO incompatible transplants (eg., bone marrow, renal, liver) revealed that clinican requests were inconsistent, such that some ordered ABO titer levels for IgG antibodies only, others ordered ABO titer levels for IgM antibodies only, and still others ordered ABO titer levels for both IgG and IgM antibodies. Consequently, he wonders what other institutions do upon receiving an order to perform an ABO isoagglutinin titer. He also wonders if there is published literature (evidence) to support the measurement of IgM ABO antibody titers over IgG ABO antibody titers (or vice versa).

Editor's Note: The previous e-Network Forum topic, The case for limiting transfusions to ABO identical red cells/platelets/FFP/ cryoprecipitate and avoiding transfusion of incompatible cell associated or soluble antigen or isoagglutinins, may be germane to this discussion.

The following comments have been received.

ADDENDA Feb. 13, 2006

1. A transfusion medicine physician in California reports that in response to the question about the use and method of determining ABO isoagglutinin titers for patients who need ABO incompatible organ transplantation, several years ago, one of the transplant programs that his blood center supports asked for help to establish a means for transplanting group A2 kidneys into O and/or B patients (and A2B kidneys into B patients). Together, they reviewed the methods of the few other programs doing this at that time and ultimately decided to base their transplant decision upon the results of a series of anti-A titers done using only DTT-treated serum--e.g., if three IgG titers done over the course of ≥ three months are all ≤ 4, the group O/B patient is considered eligible for transplant with an A2 kidney.

Of the many references they reviewed, the one that the California physician found most helpful to him was by Nelson PW et al. "Stratification and Successful Transplantation of Patients Awaiting ABO-Incompatible (A2 into B and O) Transplantation by A-Isoagglutinin-Titer Phenogroup." Transplantation Proceedings 1996;28:221-223. The authors, affiliated with the Midwest Transplant Network, used only DTT-treated anti-A1 and anti-A2 titers (and now use only anti-A1 titers) when determining the eligibility of the prospective recipient. Two more useful references subsequently published by the same group are: (1) Nelson PW et al. Transplantation 1998;65:256-260; and (2) Bryan CF. Transplantation 1998;66:1714-1717.

For another perspective, one might wish to review the article by Alkhunaizi AM et al. "Renal Transplantation across the ABO Barrier Using A2 Kidneys." Transplantation 1999; 67: 1319-1324 It describes similar A2-to-B/O kidney transplant work done by Oregon Health Sciences University though, at the time of the article, this group was using both DTT-treated (IgG) and non-DTT-treated (IgG + IgM) anti-A1 and anti-A2 titers to determine whether to transplant.

As a related aside, the California physician shares the frustration of the questioner when it comes to determining the importance of ABO isoagglutinin titers in causing hemolytic transfusion reactions associated with the transfusion of incompatible plasma (such as when a group A patient receives group O platelets). Many of the articles that the California physician has reviewed on this topic have been very unclear to him about the testing methods that were used, sometimes making it very difficult to determine the most appropriate standard of practice for deciding whether or not to defer the implicated donor from making future platelet donations.

ADDENDA Feb. 14, 2006

2. Dr. James P. AuBuchon, chair of the College of American Pathologists (CAP) Transfusion Medicine Resource Committee (TMRC) (attribution used with permission) reports that Supplemental questions are being planned for an upcoming ABT survey of the CAP to gather information regarding the reason for performing isoagglutinin titrations. For information about the ABT survey, see pages 6, 154 and 162 of the CAP's catalog "2006 Surveys & Anatomic Pathology Education Programs".

ADDENDA Feb. 20, 2006

3. W. John Judd, FIBMS, MIBiol, Professor of Immunohematology at the University of Michigan (attribution used with permission) comments that with regard to the posting of February 13, 2006 submitted by the transfusion medicine physician in California, please note that there is no such thing as anti-A2. Consequently, there is no so such thing as an anti-A2 titer!!! Group B sera contain anti-A and anti-A1. The anti-A1 can be prepared by prolonged adsorption with A2 RBCs, or rapid adsorption with A1 RBCs. The antibody eluted from A2 RBCs reacts with both A1 and A2 RBCs.

4. In response to the comments of Professor Judd, the California physician who provided the information that was posted on February 13, 2006 fully agrees that there is no such thing as a specific “anti-A2” titer.  He acknowledges using this "imprecise" expression to refer to the agglutinating titer of an individual’s serum when tested against A2 red cells. He adds that "Transplant Physicians" have used that same expression in their literature; however, those in transfusion medicine should use more precise terminology, as pointed out by Professor Judd.

ADDENDA Feb. 25, 2006

5. A transfusion medicine physician in the Pacific Northwest reports that her facility approaches the titer question for ABO incompatible organ transplantation in the following fashion:

Their reference laboratory performs ABO antibody titers as specified by UNOS when evaluating a group O or group B patient is a candidate for a group A2 kidney. As she understands the UNOS method, the serum is tested with and without DTT treatment. The titer is determined after a 10 minute room temperature incubation. If the initial titer is greater than 8, the testing is extended out to a 1:32 dilution using saline and includes a pooled group O cell as a control.

For the other transplant situations:

• With regard to ABO incompatible heart transplants to infants, she reports that the protocol used by Foreman C, Gruenwald C, West L. ABO-incompatible heart transplantation: a perfusion strategy. Perfusion 2004:19;69-72 does not differentiate between IgG ABO antibody and IgM ABO antibody titers.
• For kidneys, she reports that the protocol used by Sonneday CJ, Warren DS, Cooper M, et al. Plasmapheresis, CMV hyperimmuneglobulin, and anti-CD20 allow ABO incompatible renal transplantation without splenectomy. Am J Transplant 2004;4(8):1315-22, calls for 30 minute room temperature incubation followed by 30 minute 37 degree incubation, followed by reading at the AHG test phase, as do many Japanese protocols, and does not differentiate between IgG ABO antibody or IgM ABO antibody titers. Some centers, as per Nelson PW, Shield CF III, Muruve NA, et al. Increased access to transplantation for blood group B cadaveric waiting list candidates by using A2 kidneys: time for a new national system? Am J Transplant 2002;2(1):94-9 and the titer procedure at: http://www.mwob.org/pdfs/transplant8.pdf seem to differentiate between IgG ABO antibody and IgM ABO antibody titers, but she thinks that is because those titers are intended for the ABO incompatible A2 kidney transplant.

The responding colleague reports that she asked her institution's liver transplant chief and her laboratory's "HLA guru" if the method of determining the ABO antibody titer really makes a difference. The surgeon indicated that for liver or small bowel, he does not think it is necessary to differentiate between IgG ABO antibody and IgM ABO antibody titers. The HLA guru said that he knows of no good data to say it is necessary to discriminate. He believes that as long as the total titer is lowered for the transplant/ post-transplant period, it is probably safe for the graft. She acknowledges that her institution has never been comfortable with an "immediate spin" titer, like that done by other groups, so they have validated a titer procedure that requires a 30 minute (rather than an hour) incubation, which she believes gives a titer that is influenced by both IgM and IgG ABO antibodies.

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