Recently, a media blitz heralded the arrival of an end-stage renal disease prediction calculator for potential living kidney donors, backed up by a prestigious publication in the New England Journal of Medicine. I glanced at the study, noticed that it used the “woefully incomplete” and “useless” OPTN database, and it only pulled living kidney donors from 2005 onward. Which is not good.
You see, OPTN has been collecting (inefficiently) identifying information (aka social security number) on living donors since 1993. The Secretary of Health mandated one year of follow-up on all living donors in 2000. In addition, prior studies indicate that living kidney donors who progress to kidney failure will do so 17-20 years post-donation. These facts led me to believe that the researchers were more interested in minimizing the risk of ESRD for LKDs rather than warning us of our true probability.
And since I have written about this very topic many, MANY times in the past 7 years, I have no inclination to rehash myself. Fortunately, Steiner did much of the work for me in his editorial commentary on the published paper.
However, a recent 7.6-year study in the United States showed that the incidence of ESRD was 8 times as high among donors as among well-selected nondonor controls.2 A similar 15.2-year study in Norway showed that the risk was 11 times as high.3 The magnitude of these relative risks has been debated, but when predonation risks of ESRD are multiplied by the relative risk of donation, significantly greater absolute postdonation risks are predicted. However, the absolute rates of ESRD were low in both studies, which reinforced the prevailing “low risk” characterization of donation..
To translate a smidge: Two prior studies (which I’ve written about here) have found that living kidney donors have an 8-11x increased risk of kidney failure as compared to their healthy, matched, two-kidneyed cohort. But the pro-living donation advocates don’t like using those numbers because they’re – well – scary. Instead, they squawk about “absolute” risk, meaning that even if donating raises the chance of an individual LKD progressing to kidney failure, the incidence of ESRD in living kidney donors is low so – you know – don’t worry too much about it.
For example (and I’m pulling these numbers out of the air here), say there’s a 4 in 100 chance of developing a type of cancer, but that eating garbanzo beans increases that risk 50%. Yikes, right? In ‘absolute’ terms, that’s still only a 6 in 100 risk, which is like ‘meh’, bring on the garbanzos!
But if we were talking about smoking? If the same numbers applied, would you pick up the habit? Hmmm…
[Note: see this nice explanation of these statistical maneuvers here]
He goes on to say that the low estimates in the prior studies “may well have been underestimated” (In other words, the true risk is higher). Why?
…approximately 90% of cases occur after 44 years of age, and half the cases occur after 64 years of age.5,6 Many diseases that will cause ESRD in later life will not be present in young candidates, and screening will not detect them.
He uses diabetes, which accounts for nearly half the kidney failure currently seen in the US, as an example:
Currently, postdonation diabetes is poorly predicted in donor candidates, even with the use of focused, traditional criteria8 rather than the nonspecific risk factors used in the current study. Furthermore, ESRD would not have developed in any patient with classically progressing diabetic nephropathy during the study interval.
- The researchers included generic risk factors which have limited applicability. When I was being evaluated as a living kidney donor, I asked the nephrologist about my recipient’s expected graft survival. He stammered and said “the average graft survival is…”. Well, I didn’t want to know the “average” of every recipient under all circumstances, I wanted to know specifically about my sister. Potential living kidney donors feel the same way about their own kidney health too.
- The six-plus years this study captured is simply NOT ENOUGH TIME to know the true incidence, prevalence and risk of end-stage renal disease for kidney donors. Following them for such a short period results in a gross underestimation of disease progression.
It also allows the transplant industry to keep reassuring the public about living donation’s safety, all while emphasizing the need for living donor organs. They appear to actually care about living donor safety and well-being,when recent and distant history shows they clearly do not.
Unfortunately, I think that’s the point.
Grams ME, Sang Y, Levey AS, Matsushita K, Ballew S, Chang AR, Chow EK, Kasiske BL, Kovesdy CP, Nadkarni GN, Shalev V, Segev DL, Coresh J, Lentine KL, Garg AX, & Chronic Kidney Disease Prognosis Consortium (2015). Kidney-Failure Risk Projection for the Living Kidney-Donor Candidate. The New England journal of medicine PMID: 26544982
Steiner, R. (2015). The Risks of Living Kidney Donation New England Journal of Medicine DOI: 10.1056/NEJMe1513891