Demographic and clinical characteristics associated with glomerular filtration rates in living kidney donors

Abstract

Due to the shortage of organs, living donor acceptance criteria are becoming less stringent. An accurate determination of the glomerular filtration rate (GFR) is critical in the evaluation of living kidney donors and a value exceeding 80 ml/min per 1.73 m(2) is usually considered suitable. To improve strategies for kidney donor screening, an understanding of factors that affect GFR is needed. Here we studied the relationships between donor GFR measured by (125)I-iothalamate clearances (mGFR) and age, gender, race, and decade of care in living kidney donors evaluated at the Cleveland Clinic from 1972 to 2005. We report the normal reference ranges for 1057 prospective donors (56% female, 11% African American). Females had slightly higher mGFR than males after adjustment for body surface area, but there were no differences due to race. The lower limit of normal for donors (5th percentile) was less than 80 ml/min per 1.73 m(2) for females over age 45 and for males over age 40. We found a significant doubling in the rate of GFR decline in donors over age 45 as compared to younger donors. The age of the donors and body mass index increased over time, but their mGFR, adjusted for body surface area, significantly declined by 1.49+/-0.61 ml/min per 1.73 m(2) per decade of testing. Our study shows that age and gender are important factors determining normal GFR in living kidney donors.

Figure 1. Breakdown of prospective living kidney donors

Note: Excluded for serum creatinine prior to 1996 (n=512). CCF, Cleveland Clinic Foundation.

Figure 2. Renal function in prospective kidney donors

Plot depicting measured radiolabeled iothalamate glomerular filtration rates against donor age for each of the groups.

Figure 3. Effects of age on renal function

Influence of donor age on the slope of glomerular filtration rate in (a) women and (b) men.

Figure 4. Secular trends of renal function over 3 decades

Influence of testing era on (a) living donor age, (b) body mass index, and (c) glomerular filtration rate adjusted for body surface area.

Figure 5. Comparison of estimated GFR in two different cohorts

Mean, 5th, and 95th percentiles for expected eGFR by the re-expressed MDRD equation in living kidney donors (black lines) and eGFR by the re-expressed MDRD equation in subjects participating in the Nijmegen study (gray lines) among different age groups for (a) men and (b) women.