Panel Reactive Antibody (PRA) is a blood test that is routinely performed on patients waiting for kidney and heart transplants and measures anti-human antibodies in the blood. The PRA score is given as a percentage and can be from 0% to 99%. The PRA represents the percentage of the U.S. population that the anti-human antibody in your blood reacts with.
Patients develop anti-HLA (Human Leukocyte Antigen) antibodies from exposure to HLA of other humans through previous transplants, blood transfusions and/or pregnancy. Patients showing high Panel Reactive Antibodies are often referred to as sensitized. Patients with high PRA (usually > 50%) are less likely to receive transplants as the risk for immediate antibody-mediated rejection of the transplanted organ is significantly increased.
Treatments to reduce PRA in sensitized transplant candidates exist including treatment with Rituximab (a B-cell specific antibody), IVIg, protein A immunoabsorption, plasmapheresis etc.
Reference: Jordan and Pescovitz, Clin J Am Soc Nephrol 1: 421–432, 2006 [1].