PRA or cPRA stands for [calculated] Panel Reactive Antibodies, and unless you hold a medical degree that probably just sound like "mumbo jumbo". So what is PRA/cPRA?
In a Panel Reactive Antibody (PRA) test a lab tech will test (or combine) the antibodies found in your blood against a cluster test. This is a pool of 100 people, or rather the resemblance of what 100 other peoples white blood cells would be. The reactive part of this test is determining how your antibodies work with/against the pool of white blood cells. This allows a team of doctors to see what your body's immune system will fight, or how easy/well you can receive an organ in a pool of 100 people.
If there is no rejection of your antibodies in the pool, your PRA is 0 which basically translates to it being easy to find a donor match. On some occasions a person might have a PRA of 70 (or even 90) which means your antibodies are rejected by 70% (or 90%) of the pool. This makes finding a donor harder for that individual.
This being said, PRA is not an infallible test. The test presents many problems such as sensitization (antibodies you reject) variables being numerous, click here to see how many, and inconsistent variables (not everyone contains the same antibodies). The PRA test is a pre-formulated test sent to hospitals. This presents a issue as the sample pool may not be representative of your area (or where you choose to get a transplant). Due to these inaccuracies PRA is not a realistic measure of how difficult it is to find a donor.
Calculated Panel Reactive Antibodies (cPRA) is a more extensive testing. This testing protocol allows for a higher and more precise calculation, as the testing pool is a sum of 12,000. cPRA is more precise as it allows doctors/techs to rule out any one of the antibodies you may reject and not include those people in the pool search for a donor.
In the last few years technology (and practices) have advanced, allowing cPRA to be the more widely used test due to specificity and accuracy. A big advantage of cPRA is the exclusion of participants you would like reject. This increases the efficiency of organ allocation, there by giving transplant recipients a better chance a procuring an organ.
Organ Procurement and Transplant Network (OPTN)
List of cPRA antigens
cPRA the New Measure of Transplant Candidates