Tuesday, March 13, 2007

The Emory Algorithm

Hi everyone:

Each time we receive updated PRA numbers, I feel compelled to learn more about the whole issue of pretransplant sensitization. Often, this involves re-visiting material I've already read, but sometimes it yields new nuggets of information...and sometimes it just leads to greater confusion. I think this curiosity is a bit frustrating for Patty's doctors, because we are sometimes challenging them based on data that may be dated and therefore inaccurate, or that is contradicted by other studies. I'm not afraid to admit that I'm sure, at times, that I'm getting the information almost entirely wrong. For anyone who is curious about the nitty-gritty, below is what I've been encountering most recently.

This morning, I read a study from 1996 that showed that people with PRA levels similar to Patty's typically do not survive as long as those with low PRA levels, even if a suitable crossmatch is found. In this particular study, the three-year survival of patients with a PRA over 11% (Patty is at 100%) was 39-56%, depending on the type of sensitivity, as opposed to 76-78% for those with low PRA levels. Ultimately, do these numbers mean anything, because they were reported in 1996? We don't know, but they sure provide food for thought. Other study results suggest that the PRA numbers are too highly regarded as a factor in considering a person eligible for transplant, and that they don't ultimately factor into measures of rejection and/or survival if the crossmatch is, as desired, negative. In still another study, the results suggested that even a transplant against positive crossmatch could be performed without significant long-term consequences. Do you see the conundrum here?

I read with great interest some recent stories about a new decision process called the Emory Algorithm. In brief, this algorithm is used to help refine the process of determining whether or not a person will tolerate a transplanted organ (most often, in this case, a kidney), by identifying specific antigens that would cause a negative response to a transplanted organ. My hope was that we might find that within Patty's numbers, even though they are high, there might be some pathways to a successful transplant. With mild optimism, I contacted Patty's cardiac team; one member replied:

The Emory Algorithm, from my read, is a listing strategy where they find "unacceptable antigens" and then let the organ bank know. We do this also for highly sensitized patients; unfortunately, Patty has such numerous antibodies to preclude listing them as unacceptable.

Of course, Patty wouldn't be Patty if she didn't stand out, even among a group of people who themselves stand out because of their high PRA levels. If I understand correctly, the whole PRA mess goes beyond just the 60/100 number, to include both sensitivity (the PRA percentage) and specificity (the specific markers within those percentages that rule out, or rule in, a possible candidate). Unless I'm mistaken, Patty is pretty much off the charts in both regards.

My reading, and my hope for some magical answer, continues...


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