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Thursday, May 23, 2013
Can Abnormal Test Results Disqualify an Organ Transplant Candidate?
If a candidate for tranplantation is assessed has having abnormal test results, does this disqualify him for a transplant?
For lung transplantation, all candidates are assessed to see if they have antibodies against proteins (these proteins are called antigens) that are commonly present in others within the general population. This assessment is done with a test called a Panel of Reactive Antigens (PRA), which is performed by measuring the antibodies that a candidate's immune system generates in response to being exposed to blood or tissue from another person.
If a candidate is found to have a "high" PRA value, that means that they have several antibodies against antigens seen in the general population. Should such a candidate receive an organ from a person to whom they already have antibodies, then there would be a high risk of sudden and severe rejection of the transplanted organ. Conversely, candidates who have "low" PRA values are assessed to be at a low risk for experiencing early severe rejection because it is statistically unlikely that they would receive an organ from someone to whom they had pre-formed antibodies.
For those candidates that may have a "high" PRA value, a special matching procedure can be performed where, following identification of a specific donor, the candidate's blood is tested directly against that of the donor (as opposed to the general population) to see if the candidate has pre-formed antibodies to the specific donor. This is called a prospective crossmatch. If the prospective crossmatch is "high," then the candidate again is shown to have excessive pre-formed antibodies to the donor tissue and the transplant will likely not take place.
However, to do this test requires more time. Also, because lungs are very perishable, the need to perform this test may impact on how far a surgeon can travel to retrieve a lung from a donor whose blood would have to be tested against the blood of the candidate.
David R Nunley, MD, FCCP
Former Associate Professor
College of Medicine
The Ohio State University