Trends in the Screening and Acceptance of Living Kidney Donors

The use of living donors for kidney transplantation in the United States has become increasingly common, with recipients of a living donor kidney demonstrating better outcomes and shorter waiting times. Substantial differences exist between transplant centers in their choice of protocols and exclusion criteria for potential living donors. Nevertheless, certain trends in living donation practices over the past 20 years, reflecting a relaxation of some acceptance criteria and a tightening of others, have become apparent from surveys of transplant programs (1) and analysis of registry data collected by the United Network for Organ Sharing (UNOS) (2).

Donor-recipient relationships

One of the most dramatic trends among living donors is in the relationships between donors and recipients. Over the past 12 years, genetically unrelated, nonspousal donors have more than doubled (Figure 1). In a 1986 survey, only 16 percent of transplant programs in the United States reported that they would accept living unrelated donors—compare this to 31 percent in 1995 and 100 percent in 2007. The acceptance of nondirected (altruistic or Good Samaritan) donors has also increased, from 8 percent of programs in 1989 to 38 percent in 2000 to 61 percent in 2007.
Figure 1.

Trends in living related versus living unrelated, nonspousal donors in the United States.

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Donor age

Living kidney donors are now older. In 2008, 1.5 percent of living kidney donors were over the age of 65, compared to 0.7 percent in 1988. Between 1995 and 2007, the percentage of programs without a set upper-age limit more than doubled to 59 percent. In contrast, programs became stricter with respect to younger candidates. No programs reported an age cutoff of 14 or 16 years in 2007, and almost none reported having no lower age limit at all. Quantitatively, however, young donors are less common than older donors, so the increase in the median age of donors from 35 to 41 years between 1988 and 2008 suggests an overall trend toward less restrictive age criteria for donors.

Kidney function

Most transplant programs in the United States continue to use a 24-hour collection to measure creatinine clearance, although some use a direct measure of GFR (e.g., iodinated marker) or an estimated GFR formula. Although UNOS data suggest no statistically significant changes in the mean serum creatinine or eGFR of donors over the past decade, surveys indicate changes in specific practices. In contrast to1995, when some programs reported using lower creatinine clearance cutoffs of 60 mL/min/1.73 m2 or even 40 mL/min/1.73 m2, by 2007 no programs reported using a cutoff below 80 mL/min/1.73 m2.

Hypertension

Exclusion criteria for blood pressure have become less restrictive, although they remain highly variable among centers. In 1995, most programs excluded candidates taking antihypertensive medications or having borderline hypertension. By 2007, 47 percent of programs excluded candidates on any antihypertensive medication, but 41 percent excluded donors only if they were taking more than one medication, and 8 percent excluded donors only if they were taking more than two medications (Figure 2). This trend may be partly due to data suggesting that donation by selected patients with well-controlled hypertension appears to be safe in the short term.
Figure 2.

Exclusion criteria by category of blood pressure reported in surveys from 1995 and 2007.

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From Mandelbrot et al. (1). Abbreviation: BP = blood pressure.

Thus, significant variability remains among transplant programs in the medical criteria used to evaluate donors, but there are clear overall trends. Protocols for the evaluation of potential donors will continue to evolve as more data on outcomes emerge, especially regarding medically complex donors.

Notes

[1] Didier A. Mandelbrot, MD, is medical director of the Living Kidney Donor Program at Beth Israel Deaconess Medical Center, director of clinical trials at the Transplant Institute, and associate professor of medicine at Harvard Medical School, in Boston.

References

1. Mandelbrot DA, et al. The medical evaluation of living kidney donors: A survey of US transplant centers. Am J Transplant 2007; 7:2333–2343.

2. Davis CL, Cooper M. The state of U.S. living kidney donors. Clin J Am Soc Nephrol 2010; 5:1873–80.

May 2013 (Vol. 5, Number 5)