UAB Synopsis, Vol. 28, No. 44, November 23, 2009
UAB’s Alabama Transplant Center has added another option to its Incompatible Transplant Program in an effort to shorten the waiting list of patients who need a kidney transplant.
“Our surgeons have performed antibody desensitization and paired kidney transplants, and now we offer a subset of blood type A living donors the opportunity to donate to patients who have type O or B blood,” says Assistant Professor of Surgery Jeremy Goodman, MD.
Subtype A2, which comprises up to 20% of people with blood type A, is now recognized as a permissible barrier to cross in kidney transplantation. Subtype A2 donors are identified when red blood cells do not agglutinate with the antisera used to type for A1, Dr. Goodman says. A2 donors’ cells express a lower amount of A antigen and can be successfully transplanted across the blood group barrier. The donors are designated as “non-A1.”
The UAB Transplant Program now tests all potential living donors who have type A blood to determine their subtype, says Program Director Martha R. Tankersley, CRNP.
“The initial screening for ABO incompatibility [ABOi] with this protocol has already turned up one potential match, and over the course of a year our program hopes to find and transplant a handful of these patients,” Tankersley says.
Potential living donors identified as subtype non-A1 are tested twice to confirm the finding. Recipients are then tested multiple times before transplant to determine their level of anti-A titer. Those with a level <0.8 are potentially transplantable. It is possible, Dr. Goodman says, that the program eventually may open to patients with higher anti-A titers.
Subtype A1 patients waiting for a kidney transplant still might participate in a paired exchange, and patients who have antibodies to their living donor’s blood type may enter the hospital’s desensitization program. The desensitization program uses a variety of preconditioning therapies and other means to facilitate incompatible transplants.
“This new program adds another option, giving more of our patients hope that they can receive a kidney transplant,” Dr. Goodman says. “Renal transplants provide clear benefits over hemodialysis in terms of lifestyle, health, and cost, so our center will continue to seek every possible way to help patients receive transplantation.”
Dr. Goodman and Assistant Professor of Medicine Vineeta Kumar, MD, Division of Nephrology, are codirectors of the ABOi Program.
“Use of non-A1 kidneys for O and B recipients can increase the donor pool for blood group O and B transplant candidates and decrease their waiting times,” Dr. Kumar notes. “Moreover, this practice could increase living donor use, which can lead to better graft survival versus nonliving donor transplant.”
Tankersley, who previously managed the Kidney Transplant Program, recently was named administrative director for heart, lung, liver, kidney, and pancreas transplantation programs. Her duties also include oversight of the Transplant Data Registry Office, the Histocompatibility Laboratory, and the Children’s Hospital Transplant Program, which UAB Hospital manages.
Blood Types
The presence or lack of molecules on the surface of blood cells defines blood type. Type O has no molecules. Types A and B have a combination of two molecules that result in type A (AA or AO molecules), type B (BB or BO molecules), or type AB. When blood types are mixed, the molecules act as antigens that trigger an ABO incompatibility reaction. To reduce the reaction blood types typically must be matched or patients must undergo desensitization measures.