COVID-19 Vaccine Seroresponse Based on The Timing of The Primary Series; Pre- versus Post-Renal Transplantation.

BACKGROUND: Coronavirus disease 2019 (COVID-19) poses a serious risk to patients with chronic kidney disease (CKD) and renal transplant. While COVID-19 vaccination is recommended before transplant, there are limited data comparing vaccine timing. Our aim is to evaluate serological responses to COVID-19 vaccines pre- and post-renal transplant and the durability of antibody levels. METHODS: We retrospectively evaluated the antibody response of adult renal transplant recipients who had received at least a primary series of the COVID-19 vaccine. The patients were divided into two groups based on the timing; pre- or post-transplant. Antibody titer levels were evaluated at least 4 weeks after vaccination for each group. Titer durability was assessed by calculating the median titer level of individuals. RESULTS: A total of 139 patients were identified between January 2019 and April 2022. Twenty-nine patients were excluded because of previous COVID-19 infection, and 15 patients were excluded each for insufficient vaccine doses and lack of titer data. Forty patients were included for the pre-transplant group and 40 for post-transplant. The number of pre-transplant patients who developed antibodies (39 patients, 97.5%) was significantly greater than the number of post-transplant patients (21 patients, 52.5%) with p < .01. The median post-vaccination titer levels were significantly greater in the pre-transplant group up to 5 months after vaccination (p < .05). The pre-transplant group's titers seemed sustained even after renal transplantation. CONCLUSION: Vaccinating renal transplant patients before transplant results in increased achievement of seroresponse, higher levels of antibody titers, and sustained titers following transplant. Larger and prospective studies are warranted to confirm the findings.

Outcomes of kidney donors with sickle cell trait: A preliminary analysis.

Most transplant centers do not screen kidney donor candidates for sickle cell trait (SCT) and many decline candidates with SCT since it may associate with kidney disease. We compared 17 kidney donors with SCT to propensity score matched donor controls on mortality, reduced eGFR, proteinuria and kidney failure. The prevalence of SCT in African American (AA) donors was 11 per 1000 compared to 73 per 1000 in non-donor AA. Donors with SCT were younger; 33 versus 35 years in controls, nine were AA, six were White, and two were listed as other or unknown ethnicities. After a follow-up period of 18.2 ± 10.5 years, the proportions of donors with SCT and controls who were alive, developed hypertension or cardiovascular disease were similar. No donor with SCT developed an eGFR <30 mL/min/1.73 m2 or kidney failure. SCT was, however, associated with increased risk of proteinuria; RR 5.71 (95% CI 5.7 - 22.7), P = .01. This small and preliminary case series suggest that donors with SCT should perhaps be considered more often provided they were aware of the lack of evidence to support liberal acceptance and that these outcomes reported here likely represent a healthy cohort of donors with SCT.

Intermediate Renal Outcomes, Kidney Failure, and Mortality in Obese Kidney Donors.

BACKGROUND: Obesity is associated with the two archetypal kidney disease risk factors: hypertension and diabetes. Concerns that the effects of diabetes and hypertension in obese kidney donors might be magnified in their remaining kidney have led to the exclusion of many obese candidates from kidney donation. METHODS: We compared mortality, diabetes, hypertension, proteinuria, reduced eGFR and its trajectory, and the development of kidney failure in 8583 kidney donors, according to body mass index (BMI). The study included 6822 individuals with a BMI of <30 kg/m2, 1338 with a BMI of 30-34.9 kg/m2, and 423 with a BMI of ≥35 kg/m2. We used Cox regression models, adjusting for baseline covariates only, and models adjusting for postdonation diabetes, hypertension, and kidney failure as time-varying covariates. RESULTS: Obese donors were more likely than nonobese donors to develop diabetes, hypertension, and proteinuria. The increase in eGFR in obese versus nonobese donors was significantly higher in the first 10 years (3.5 ml/min per 1.73m2 per year versus 2.4 ml/min per 1.73m2 per year; P<0.001), but comparable thereafter. At a mean±SD follow-up of 19.3±10.3 years after donation, 31 (0.5%) nonobese and 12 (0.7%) obese donors developed ESKD. Of the 12 patients with ESKD in obese donors, 10 occurred in 1445 White donors who were related to the recipient (0.9%). Risk of death in obese donors was not significantly increased compared with nonobese donors. CONCLUSIONS: Obesity in kidney donors, as in nondonors, is associated with increased risk of developing diabetes and hypertension. The absolute risk of ESKD is small and the risk of death is comparable to that of nonobese donors.

Financial Hardship Among Nonelderly Adults With CKD in the United States.

RATIONALE & OBJECTIVE: The burden of financial hardship among individuals with chronic kidney disease (CKD) has not been extensively studied. Therefore, we describe the scope and determinants of financial hardship among a nationally representative sample of adults with CKD. STUDY DESIGN: Cross-sectional. SETTING & PARTICIPANTS: Nonelderly adults with CKD from the 2014-2018 National Health Interview Survey. EXPOSURE: Sociodemographic and clinical characteristics. OUTCOME: Financial hardship based on medical bills and consequences of financial hardship (high financial distress, food insecurity, cost-related medication nonadherence, delayed/forgone care due to cost). Financial hardship was categorized into 3 levels: no financial hardship, financial hardship but able to pay bills, and unable to pay bills at all. Financial hardship was then modeled in 2 different ways: (1) any financial hardship (regardless of ability to pay) versus no financial hardship and (2) inability to pay bills versus no financial hardship and financial hardship but able to pay bills. ANALYTICAL APPROACH: Nationally representative estimates of financial hardship from medical bills were computed. Multivariable logistic regression models were used to examine the associations of sociodemographic and clinical factors with the outcomes of financial hardship based on medical bills. RESULTS: A total 1,425 individuals, representing approximately 2.1 million Americans, reported a diagnosis of CKD within the past year, of whom 46.9% (95% CI, 43.7%-50.2%) reported experiencing financial hardship from medical bills; 20.9% (95% CI, 18.5%-23.6%) reported inability to pay medical bills at all. Lack of insurance was the strongest determinant of financial hardship in this population (odds ratio, 4.06 [95% CI, 2.18-7.56]). LIMITATIONS: Self-reported nature of CKD diagnosis. CONCLUSIONS: Approximately half the nonelderly US population with CKD experiences financial hardship from medical bills that is associated strongly with lack of insurance. Evidence-based clinical and policy interventions are needed to address these hardships.

Long-term outcomes of kidney donors with fibromuscular dysplasia.

BACKGROUND: Fibromuscular dysplasia (FMD) is a non-atherosclerotic systemic arterial disease that is not infrequently discovered during kidney donor evaluation. Current guidelines do not provide recommendations regarding the use of kidneys from donors with FMD and there is a paucity of data on the outcomes of these donors. METHODS: The Renal and Lung Living Donor Evaluation (RELIVE) study addressed long-term outcomes of 8922 kidney donors who donated between 1963 and 2007. We compared the development of hypertension, cardiovascular disease (CVD), proteinuria and reduced estimated glomerular filtration rate (eGFR) in 113 kidney donors with FMD discovered during donor evaluation versus 452 propensity score matched donors without FMD. Outcomes modeling with logistic and Cox regression analysis and Kaplan-Meier statistics were performed. RESULTS: Donors with FMD were older (51 versus 39 years), were more likely to be women (80% versus 56%) and had a higher systolic blood pressure at donation (124.7 versus 121.3 mmHg) (P < 0.05 for all). After a mean ± standard deviation follow-up of 15.5 ± 8.9 years, a similar proportion of donors with and without FMD were alive, and developed hypertension (22.2% versus 19.8%), proteinuria (20.6% versus 13.7%) and CVD (13.3% versus 13.5%). No donor with FMD developed an eGFR <30 mL/min/1.73 m2 or end-stage kidney disease. The multivariable risk of mortality, CVD and renal outcomes in donors with FMD was not elevated. CONCLUSIONS: Kidney donors with FMD appear to do well, do not appear to incur increased risks of hypertension, proteinuria, CVD or reduced eGFR, and perhaps carefully selected candidates with FMD can safely donate as long as involvement of other vascular beds is ruled out.

Outcomes of kidney donors with pre- and post-donation kidney stones.

Roughly 25% of US transplant centers exclude donor candidates with kidney stones fearing future obstructive consequences and the possible association between stones and CKD. We compared the development of hypertension, proteinuria, and reduced eGFR in 227 kidney donors with kidney stones to 908 propensity score-matched donor controls without kidney stones using data from The Renal and Lung Donor Evaluation (RELIVE) Study which studied intermediate and long-term outcomes of 8922 donors who donated between 1963 and 2007. 200 donors had kidney stones prior to donation, 21 had post-donation stones, and 6 had pre- and post-donation stones. Donors with stones were older, more likely to be Caucasian, less likely to be related to the recipient and had a higher fasting glucose. After 16.5 ± 10.9 years (range 0-44 years) from donation to study close, no ESKD occurred in donors with stones. The multivariable risks of hypertension, proteinuria, and reduced GFR were similar in donors with and without kidney stones. We could not demonstrate an association between stones and adverse renal outcomes in kidney donors, and the occurrence of post-donation stones was distinctly rare. These data may provide a rationale for possibly a wider acceptance of donor candidates with low kidney stones burden.

Hypertension and renal outcomes in normotensive kidney donors with multiple renal arteries.

Having multiple renal arteries (MRA) has been linked to hypertension development. Whether kidney donors who are left with MRA in the nondonated kidney incur a higher risk of hypertension has not been studied. We compared the development of hypertension, reduced estimated glomerular filtration rate (eGFR), cardiovascular disease, and mortality in 2624 normotensive kidney donors with MRA in the nondonated kidney and to 2624 propensity score matched normotensive donor controls with a single renal artery. In total, 35% of donors had MRA. Donors with MRA were less likely to have undergone a left nephrectomy (51% vs. 83%). Postdonation hypertension was associated with age, male gender, non-White ethnicity, obesity, and family history of hypertension. Having MRA was not associated with risk of hypertension; aHR 0.92 (95% CI 0.82-1.03), P = 0.16. After 17 ± 11 years from donation, a similar proportion of donors with and without MRA developed cardiovascular disease, proteinuria and eGFR <30, <45 and <60 mL/min/1.73 m2 and the multivariable risks of developing these outcomes were similar in the two groups. Our study did not show increased risk for hypertension, reduced eGFR, proteinuria or cardiovascular disease in donors with MRA in the remaining kidney and without hypertension at donation.

KDOQI US Commentary on the 2017 KDIGO Clinical Practice Guideline on the Evaluation and Care of Living Kidney Donors.

Living kidney donation is widely practiced throughout the world. During the past 2 decades, various groups have provided guidance about the evaluation and care of living donors. However, during this time, our knowledge in the field has advanced substantially and many agreed on the need for a comprehensive, unifying document. KDIGO (Kidney Disease: Improving Global Outcomes) addressed this issue at an international level with the publication of its clinical practice guideline on the evaluation and care of living kidney donors. The KDIGO work group extensively reviewed the available literature and wrote a series of guideline recommendations using various degrees of evidence when available. As has become recent practice, NKF-KDOQI (National Kidney Foundation-Kidney Disease Outcomes Quality Initiative) convened a work group to provide a commentary on the KDIGO guideline, with a focus on how these recommendations apply in the context of the United States. In the United States, the United Network for Organ Sharing (UNOS) guides and regulates the practice of living kidney donation. While the KDIGO guideline for the care of living kidney donors and UNOS policy are similar in most aspects of the care of living kidney donors, several important areas are not consistent or do not align with common practice by US transplantation programs in areas in which UNOS has not set specific policy. For the time being, and recognizing the value of the KDIGO guidelines, US transplantation programs should continue to follow UNOS policy.

Financial burden associated with time to return to work after living kidney donation.

Many living kidney donors undertake a significant financial burden in order to donate. We studied the association between time to return to work and reported financial burden. Kidney donors who donated from 2/2005 through 12/2015 (n = 1012) were surveyed 6 months after donation and asked about occupation, time to return to work, and financial burden (on a 10-point Likert scale). Of 856 donors working for pay, 629 (73%) responded. After adjusting for donor characteristics, increased length of time to return to work was a significant predictor of financial burden (P < .001). It is notable that those in manual/skilled trade occupations, compared with all other occupations, experienced greater financial burden for each week away from work (P = .003). Older age at donation and nondirected (vs directed) donation were associated with significantly decreased financial burden. These observations provide additional information to better inform donor candidates, and further emphasize the need to develop policies so that living kidney donation can be financially neutral.

Long-term psychosocial outcomes after nondirected donation: A single-center experience.

Short-term studies have demonstrated that nondirected donors (NDDs) have psychosocial outcomes that are similar to donors who donate directly, but long-term studies have not been done. NDDs at our center were surveyed regarding motivation; support during donation; stress related to donation; regret; financial resources used for donation; preferences about communication with the recipient; and cost reimbursement. Of 100 NDDs who donated at our center in the last 20 years, 95 remain in contact with us, and 77 responded to our survey (mean ± standard deviation [SD] 6.7 ± 4 years postdonation). The most common motivation for donation was the desire to help another (99%). Many NDDs received support from family, friends, and employers. NDDs voiced stress about the possibility of recipient kidney rejection, physical consequences to themselves, and financial burden. Only one donor expressed regret. Almost half wanted some recipient information at donation; 61% preferred routine recipient status updates; 56% believed meeting the recipient should occur at any mutually agreeable time; and 55% endorsed reimbursement for expenses. Stressors for NDDs are analogous to those of directed donors; NDDs prefer having some information about the recipient and prefer to be given a choice regarding the timing for communication with the recipient. NDDs supported donation being financially neutral.

GFR ≤25 years postdonation in living kidney donors with (vs. without) a first-degree relative with ESRD.

An increased risk of ESRD has been reported for living kidney donors, and appears to be higher for those donating to a relative. The reasons for this are not clear. One possibility is that ESRD is due to the nephrectomy-related reduction in GFR, followed by an age-related decline that may be more rapid in related donors. Between 1/1/1990 and 12/31/2014, we did 2002 living donor nephrectomies. We compared long-term postdonation eGFR trajectory for donors with (n = 1245) vs. without (n = 757) a first-degree relative with ESRD. Linear mixed-effects models were used to model the longitudinal trajectory of eGFR. With all other variables held constant, we noted a steady average increase in eGFR until donors reached age 70: 1.12 (95% CI: 0.92-1.32) mL/min/1.73m² /yr between 6 weeks and 5 years postdonation; 0.24 (0.00-0.49) mL/min/1.73m² /yr between 5 and 10 years; and 0.07 (-0.10 to +0.25) mL/min/1.73m² /yr between 10 and 20 years for donors with attained age less than 70. After age 70, eGFR declined. After we adjusted for predonation factors, the difference in eGFR slopes between related and unrelated donors was 0.20 mL/min/1.753 m2 /year (0.07-0.33). Our data suggests that postdonation, kidney donor eGFR increases each year for a number of years and that eGFR trajectory does not explain any increase in ESRD after donation.

Causes and timing of end-stage renal disease after living kidney donation.

End-stage renal disease (ESRD) is a risk after kidney donation. We sought, in a large cohort of kidney donors, to determine the causes of donor ESRD, the interval from donation to ESRD, the role of the donor/recipient relationship, and the trajectory of the estimated GFR (eGFR) from donation to ESRD. From 1/1/1963 thru 12/31/2015, 4030 individuals underwent living donor nephrectomy at our center, as well as ascertainment of ESRD status. Of these, 39 developed ESRD (mean age ± standard deviation [SD] at ESRD, 62.4 ± 14.1 years; mean interval between donation and ESRD, 27.1 ± 9.8 years). Donors developing ESRD were more likely to be male, as well as smokers, and younger at donation, and to have donated to a first-degree relative. Of donors with a known cause of ESRD (n = 25), 48% was due to diabetes and/or hypertension; only 2 from a disease that would have affected 1 kidney (cancer). Of those 25 with an ascertainable ESRD cause, 4 shared a similar etiology of ESRD with their recipient. Almost universally, thechange of eGFR over time was stable, until new-onset disease (kidney or systemic). Knowledge of factors contributing to ESRD after living kidney donation can improve donor selection and counseling, as well as long-term postdonation care.

Hypertension after kidney donation: Incidence, predictors, and correlates.

Incidence of postdonation hypertension, risk factors associated with its development, and impact of type of treatment received on renal outcomes were determined in 3700 kidney donors. Using Cox proportional hazard model, adjusted hazard ratios (HRs) for cardiovascular disease (CVD); estimated glomerular filtration rate (eGFR) <60, <45, <30 mL/min/1.73m2 ; end stage renal disease (ESRD); and death in hypertensive donors were determined. After a mean (standard deviation [SD]) of 16.6 (11.9) years of follow-up, 1126 (26.8%) donors developed hypertension and 894 with known antihypertensive medications. Hypertension developed in 4%, 10%, and 51% at 5, 10, and 40 years, respectively, and was associated with proteinuria, eGFR < 30, 45, and 60 mL/min/1.73m2 , CVD, and death. Blood pressure was <140/90 mm Hg at last follow-up in 75% of hypertensive donors. Use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (compared to other antihypertensive agents) was associated with a lower risk for eGFR <45 mL/min/1.73m², HR 0.64 (95% confidence interval [CI] 0.45-0.9), P = .01, and also less ESRD; HR 0.03 (95% CI 0.001-0.20), P = .004. In this predominantly Caucasian cohort, hypertension is common after donation, well controlled in most donors, and factors associated with its development are similar to those in the general population.

Weight gain after kidney donation: Association with increased risks of type 2 diabetes and hypertension.

In the general population, obesity is associated with an increased risk of developing hypertension (HTN), type 2 diabetes mellitus (DM), and end-stage renal disease (ESRD). Therefore, most transplant centers have a body mass index (BMI) threshold for accepting living kidney donors. But there have been no studies of postdonation weight gain trends and any associated risks. We tracked serial BMIs in 940 donors for a median (IQ range) follow-up of 22.3 (15.4-35.8) years. We studied the impact of postdonation weight gain in a model adjusted for family history of HTN or DM. Donor characteristics included age, sex, smoking, fasting blood glucose, eGFR, systolic and diastolic BP, and BMI at time of donation and time postdonation. Postdonation weight gain was associated with a significant increase in the relative risk of developing HTN RR 1.93 (95% CI 1.51-2.46) (P < 0.001) and/or DM RR 4.18 (95% CI 2.05-8.5) (P < 0.0001), but not (to date) cardiovascular disease (CVD), reduced eGFR or death. Like the general population, donors gained weight as they aged; a higher BMI was associated with higher incidence of DM and HTN. Postdonation care should include ongoing counseling on the risks of substantial weight gain.

Return to normal activities and work after living donor laparoscopic nephrectomy.

Transplant programs inform potential donors that they should be able to return to normal activities within ~2 weeks and to work by 6 weeks after laparoscopic nephrectomy. We studied actual time. Between 10/2004 and 9/2014, 911 donors having laparoscopic nephrectomy were surveyed 6 months post-donation. Surveys asked questions specific to their recovery experience, including time to return to normal activities and work and a description of their recovery time relative to pre-donation expectations. Of the 911, 646 (71%) responded: mean age at donation was 43.5±10.6 years; 65% were female, 95% were white, 51% were biologically related to their recipient, and 83% reported education beyond high school. Of the 646 respondents, a total of 35% returned to normal activities by 2 weeks post-donation; 79% by 4 weeks post-donation; 94% by 5-6 weeks; however, 6% took >6 weeks. Of the 646, 551 (85%) were working for pay; of these, mean time to return to work was 5.3±2.8 weeks; median, 5 weeks. Of the 551, a total of 14% returned to work in 1-2 weeks, 46% by 3-4 weeks, and 76% by 5-6 weeks. Importantly, 24% required >6 weeks before returning to work with the highest rates for donors in manual labor or a skilled trade. Significantly longer return to work was reported by females (vs males; P=.01), those without (vs those with) post-high school education (P=.010, those with longer hospital stay (P=.01), and those with a postoperative complication (P=.02). Of respondents, 37% described their recovery time as longer than expected. During the donor informed consent process, additional emphasis on realistic expectations around recovery to baseline activities and return to work is warranted.

Renal Function Profile in White Kidney Donors: The First 4 Decades.

Previous studies reported the risk of ESRD after kidney donation, but not the renal outcomes that precede ESRD. Here, we estimated the risk of proteinuria, reduced GFR, and ESRD in 3956 white kidney donors, assessed the contribution of postdonation hypertension and diabetes to these outcomes, and developed a risk calculator. After a mean±SD follow-up of 16.6±11.9 years, 215 (6.1%) donors developed proteinuria. Men had a higher risk of proteinuria (hazard ratio [HR], 1.56; 95% confidence interval [95% CI], 1.18 to 2.05; P<0.001) as did those with higher body mass index (HR, 1.10; 95% CI, 1.06 to 1.13; P<0.001). In all, 1410 (36%) donors reached an eGFR<60 ml/min per 1.73 m(2), and 112 (2.8%) donors had either an eGFR<30 ml/min per 1.73 m(2) or ESRD (28 donors developed ESRD). An eGFR<30 ml/min per 1.73 m(2) or ESRD associated with older age (HR, 1.07; 95% CI, 1.05 to 1.09; P<0.001), higher body mass index (HR, 1.08; 95% CI, 1.04 to 1.13; P<0.001), and higher systolic BP (HR, 1.02; 95% CI, 1.00 to 1.04; P=0.01) at donation. Postdonation diabetes and hypertension associated with a fourfold higher risk of proteinuria and a >2-fold higher risk of ESRD. Models predicting proteinuria and reduced eGFR performed well (C-index 0.77-1.00). In conclusion, severe reduction in GFR and ESRD after kidney donation were uncommon and were highly associated with postdonation diabetes and hypertension. Furthermore, information available before donation may predict long-term renal outcomes in white living kidney donors.

Outcomes of kidney retransplantation in recipients with prior post-transplant lymphoproliferative disorder.

Post-transplant lymphoproliferative disease (PTLD) is an uncommon but serious complication of solid organ transplantation. Reduction in immunosuppression is the mainstay of PTLD treatment, but it may precipitate graft loss. Retransplantation remains controversial, as immunosuppression resumption may trigger PTLD relapse. Herein, we describe the experience of eight patients who underwent kidney retransplantation after successful PTLD treatment. Epstein-Barr virus (EBV) serology was not known before the first transplantation. PTLD was diagnosed 62.5 months (range 5-323 months) after transplantation and was confined to the renal allograft (n = 1), lymph nodes (n = 2), gastrointestinal tract (n = 4), or central nervous system (n = 1). Immunosuppression tapering (8/8), chemotherapy (6/8), oral cavity lymphoma excision (1/8), and allograft nephrectomy (1/8) led to hematological remission in all patients. Retransplantation was performed at a median of 55.5 months (range 29-95 months) after PTLD diagnosis. After a median follow-up of 62.5 months (range 2-125 months) allograft survival was 87.5% (seven functioning grafts, one failed graft from chronic rejection), with no recurrence of PTLD. In all, five patients remain alive; the other three died from causes other than PTLD. In conclusion, kidney retransplantation appears to be safe in patients with prior PTLD and without major risk of hematological recurrence provided that PTLD has remitted.

The renin-aldosterone axis in kidney transplant recipients and its association with allograft function and structure.

The level of the renin-angiotensin-aldosterone system (RAAS) activity in kidney transplant recipients has not been extensively studied or serially profiled. To describe this axis and to determine its association with glomerular filtration rate (GFR) change, interstitial expansion, and end-stage renal disease (ESRD), we measured plasma renin activity (PRA) and plasma aldosterone levels annually for 5 years in 153 kidney transplant recipients randomly assigned to losartan or placebo. PRA and plasma aldosterone levels were in the normal range at all times and did not vary by immunosuppression regimen. Those on losartan exhibited higher PRA but similar plasma aldosterone levels. Neither baseline nor serial PRA or plasma aldosterone levels were associated with GFR decline, proteinuria, or interstitial expansion. Losartan use (hazard ratio (HR) 0.48 (95% confidence interval (CI) 0.21-1.0), insignificant) and Caucasian donor (HR 0.18 (95% CI 0.07-0.4) significant) were associated with less doubling of serum creatinine, death, or ESRD. Hypertension, <3 human leukocyte antigen matches, the combination of tacrolimus-rapamycin, and acute rejection were associated with more events. Neither PRA nor plasma aldosterone levels were independently associated with this outcome. Higher serial plasma aldosterone levels were associated, however, with a significantly higher risk of ESRD (HR 1.01 (95% CI 1.00-1.02)). Thus, systemic RAAS is not overly activated in kidney transplant recipients, but this may not reflect the intrarenal system. Importantly, plasma aldosterone levels may be associated with more ESRD.

Cystatin C enhances glomerular filtration rate estimating equations in kidney transplant recipients.

BACKGROUND: The glomerular filtration rate (GFR) estimating equation incorporating both cystatin C and creatinine perform better than those using creatinine or cystatin C alone in patients with reduced GFR. Whether this equation performs well in kidney transplant recipients cross-sectionally, and more importantly, over time has not been addressed. METHODS: We analyzed four GFR estimating equations in participants of the Angiotensin II Blockade for Chronic Allograft Nephropathy Trial (NCT 00067990): Chronic Kidney Disease Epidemiology Collaboration equations based on serum cystatin C and creatinine (eGFR (CKD-EPI-Creat+CysC)), cystatin C alone (eGFR (CKD-EPI-CysC)), creatinine alone (eGFR (CKD-EPI-Creat)) and the Modification of Diet in Renal Disease study equation (eGFR (MDRD)). Iothalamate GFR served as a standard (mGFR). RESULTS: mGFR, serum creatinine, and cystatin C shortly after transplant were 56.1 ± 17.0 ml/min/1.73 m(2), 1.2 ± 0.4 mg/dl, and 1.2 ± 0.3 mg/l respectively. eGFR (CKD-EPI-Creat+CysC) was most precise (R(2) = 0.50) but slightly more biased than eGFR (MDRD); 9.0 ± 12.7 versus 6.4 ± 15.8 ml/min/1.73 m(2), respectively. This improved precision was most evident in recipients with mGFR >60 ml/min/1.73 m(2). For relative accuracy, eGFR (MDRD) and eGFR (CKD-EPI-Creat+CysC) had the highest percentage of estimates falling within 30% of mGFR; 75.8 and 68.9%, respectively. Longitudinally, equations incorporating cystatin C most closely paralleled the change in mGFR. CONCLUSION: eGFR (CKD-EPI-Creat+CysC) is more precise and reflects GFR change over time reasonably well. eGFR (MDRD) had superior performance in recipients with mGFR between 30 and 60 ml/min/1.73 m(2).