PRA, HLA, and Cross Matching – The headache of being hella sensitized

Every month I have my pra (panel reactive antibody) tested. The score goes from 0-100 and is a percentage. The higher the number, the harder it is to match the patient to a donor.  My score never changes:  it is 99.  This means that I am sensitized; a term that you never want to hear your transplant physician say.  As it was  explained to me by my coordinator, if 100 possible donors exist, only 1 out of the 100 might match me.

“What exactly is the pra blood test actually measuring?” you might ask.  Well, I’ll try to explain it to you in the simplest of terms and to the best of my ability.

Every person born with a functioning immune system has the ability to detect foreign organisms, attack them, destroy them, and then remember how to obliterate that specific foreign organism if it tries to invade our body again.  Our bodies create antibodies that are “keyed” to the specific foreign body.  Our immune system uses identifiers on the exterior of the non-self cells called antigens.  Antibodies are your body’s army that seek out the visible antigens and irradicate non-self cells that the antigens are attached to.   The cool part is that within that army of antibodies, each soldier is programmed to kill a specific foreign organism that your body has encountered and defeated previously.  The antibody and antigen act as a key and lock.  

Another reason we have antibodies is due to foreign human tissue or non-self cells in our bodies.  These antigens are called HLA – human leukocyte antigen. This typically happens due to blood transfusions, pregnancies, and previous transplants.  Our bodies react to the specific antigens in the foreign tissue and create specific antibodies.  The more transfusions, pregnancies, and transplants a patient has experienced, the more antigens the patient has been exposed to and the more antibodies the patient’s immune system will have created.  When a transplant patient is sensitized, that means that antibodies (keys) were present in their blood serum that fit with the antigens (locks) in a selection of the most common antigens in a cross section of the population.  PRA gives a transplant patient a broad idea of how easily they will be matched to a donor organ.

Once a matched organ becomes available, it still isn’t clear sailing.  The nurse coordinator will call you and instruct you to come to the hospital.  Once there, you will have what is called a cross match blood test performed.  This test matches your specific antibodies to the donor’s specific HLA.  If the test is negative, then the transplant surgery will proceed.

My understanding is that a patient with a PRA score of 20% is considered sensitized.  As my score is 99%, I am highly sensitized.  My doctors all assure me that this doesn’t mean I will never be transplanted.  It just means that I will have a MUCH longer wait on the transplant list.  My nephrologist pointed out that the upside is that when an organ becomes available that does match me, it will be an almost perfect fit.  The donor organ will be almost exactly like me all the way down to the molecular level.  That’s my silver lining.

I know that was as clear as mud, right?  I have done my best though and hopefully you have a clearer understanding of how you are matched to a donor organ or why it is taking so long to be matched to an organ.

Grin.  Grit.  And bear it.  In the meantime, enjoy your life and hug your lovies.