Allyson Hart

OPTN/SRTR 2015 Annual Data Report: Kidney

The first full year of data after implementation of the new kidney allocation system reveals an increase in deceased donor kidney transplants among black candidates and those with calculated panel‐reactive antibodies 98%–100%, but a decrease among candidates aged 65 years or older. Data from 2015 also demonstrate ongoing positive trends in graft and patient survival for both deceased and living donor kidney transplants, but the challenges of a limited supply of kidneys in the setting of increasing demand remain evident. While the total number of patients on the waiting list decreased for the first time in a decade, this was due to a combination of a decrease in the number of candidates added to the list and an increase in the number of candidates removed from the list due to deteriorating medical condition, as well as an increase in total transplants. Deaths on the waiting list remained flat, but this was likely because of an increasing trend toward removing inactive candidates too sick to undergo transplant.

New National Allocation Policy for Deceased Donor Kidneys in the United States and Possible Effect on Patient Outcomes

In 2013, the Organ Procurement and Transplantation Network in the United States approved a new national deceased donor kidney allocation policy that introduces the kidney donor profile index (KDPI), which gives scores of 0%-100% based on 10 donor factors. Kidneys with lower KDPI scores are associated with better post-transplant survival. Important features of the new policy include first allocating kidneys from donors with a KDPI≤20% to candidates in the top 20th percentile of estimated post-transplant survival, adding waiting time from dialysis initiation, conferring priority points for a calculated panel-reactive antibody (CPRA)>19%, broader sharing of kidneys for candidates with a CPRA≥99%, broader sharing of kidneys from donors with a KDPI>85%, eliminating the payback system, and allocating blood type A2 and A2B kidneys to blood type B candidates. We simulated the distribution of kidneys under the new policy compared with the current allocation policy. The simulation showed increases in projected median allograft years of life with the new policy (9.07 years) compared with the current policy (8.82 years). With the new policy, candidates with a CPRA>20%, with blood type B, and aged 18-49 years were more likely to undergo transplant, but transplants declined in candidates aged 50-64 years (4.1% decline) and ≥65 years (2.7% decline). These simulations demonstrate that the new deceased donor kidney allocation policy may improve overall post-transplant survival and access for highly sensitized candidates, with minimal effects on access to transplant by race/ethnicity and declines in kidney allocation for candidates aged ≥50 years.

Cardiovascular risk assessment in kidney transplantation

Cardiovascular disease (CVD) remains the most common cause of death after kidney transplantation worldwide, with the highest event rate in the early postoperative period. In an attempt to address this issue, screening for CVD prior to transplant is common, but the clinical utility of screening asymptomatic transplant candidates remains unclear. A large degree of variation exists among both transplant center practice patterns and clinical practice guidelines regarding who should be screened, and opinions are based on mixed observational data with great potential for bias. In this review, we discuss the potential risks, benefits, and evidence for screening for CVD in kidney transplant candidates, and also the next steps to better evaluate and treat asymptomatic kidney transplant candidates.

Cystatin C and Frailty in Older Men

To determine whether higher cystatin C would be associated with greater frailty in men aged 65 and older.

Uric acid and allograft loss from interstitial fibrosis/tubular atrophy: post hoc analysis from the angiotensin II blockade in chronic allograft nephropathy trial.

Background Uric acid has been linked to the progression of native kidney disease. Studies evaluating its contribution to allograft function in kidney transplant recipients, among whom hyperuricemia is common, have yielded mixed results. Methods We evaluated the association between baseline uric acid and the primary composite outcome of doubling of interstitium or ESRD from interstitial fibrosis and tubular atrophy (IF/TA) in the Angiotensin II Blockade for Chronic Allograft Nephropathy (ABCAN) Trial participants. Subjects underwent uric acid, iothalamte GFR, and urine albumin to creatinine (ACR) measurements annually for 5 years in addition to an allograft biopsy at baseline and 5 years. Results Baseline uric acid was 5.57±1.48 mg/dL; male sex, higher BMI, diuretic use, and lower GFR were associated with higher uric acid, whereas older age, less than 3 HLA matches and having a female donor were associated with lower levels. In multivariate analysis adjusting for baseline GFR, uric acid was associated with doubling of interstitium or ESRD from IF/TA (OR 1.83, 95% CI, 1.06–3.17, P=0.03). Over time, a 1 mg/dL increase in time-varying uric acid was associated with a 2.39 mL/min lower final GFR (P<0.001) but not with the secondary outcome of creatinine doubling, ESRD, or death. Conclusions These data suggest that uric acid is associated with IF/TA and thus may be a viable target for intervention.

OPTN/SRTR 2015 Annual Data Report: Early effects of the new kidney allocation system

In December 2014, a new kidney allocation system (KAS) was implemented in the United States in an attempt to improve access to transplant for historically underrepresented groups, and to incorporate longevity matching such that donor kidneys with the longest projected graft survival are given to recipients with the longest projected patient survival. The development of organ allocation policies is often guided by simulated allocation models, computer programs that simulate the arrival of donated organs and new candidates on the waiting list over a 1‐year period to project outcomes under a new allocation method. We examined the early outcomes under the new KAS using quarterly data beginning in 2013, revealing whether trends were already underway before implementation. Quarterly data also serve to reveal any bolus effect, or a rapid rise or fall in the proportion of transplants in a given group due to reordering of the list, followed by tapering toward a new steady state. Post‐KAS changes were notable for an increase in the proportion of transplants among younger candidates, black and Hispanic candidates, highly sensitized candidates, and those on dialysis for at least 5 years. Transplants among blood type B candidates increased slightly but these candidates remain underrepresented relative to their prevalence on the waiting list. Regional and national sharing increased under the new KAS, but transplants of kidneys with a kidney donor profile index above 85% decreased. Early graft survival appears unchanged, but given the increases in regional sharing, cold ischemia time, and transplants among highly sensitized candidates and candidates with long pretransplant dialysis time, long‐term graft survival will need to monitored.

Predicting Outcomes on the Liver Transplant Waiting List in the United States: Accounting for Large Regional Variation in Organ Availability and Priority Allocation Points

Background The probability of liver transplant and death on the waiting list in the United States varies greatly by donation service area (DSA) due to geographic differences in availability of organs and allocation of priority points, making it difficult for providers to predict likely outcomes after listing. We aimed to develop an online calculator to report outcomes by region and patient characteristics. Methods Using the Scientific Registry of Transplant Recipients database, we included all prevalent US adults aged 18 years or older waitlisted for liver transplant, examined on 24 days at least 30 days apart over a 2-year period. Outcomes were determined at intervals of 30 to 365 days. Outcomes are reported by transplant program, DSA, region, and the nation for comparison, and can be shown by allocation or by laboratory model for end-stage liver disease (MELD) score (6-14, 15-24, 25-29, 30-34, 35-40), age, and blood type. Results Outcomes varied greatly by DSA; for candidates with allocation MELD 25-29, the 25th and 75th percentiles of liver transplant probability were 30% and 67%, respectively, at 90 days. Corresponding percentiles for death or becoming too sick to undergo transplant were 5% and 9%. Outcomes also varied greatly for candidates with and without MELD exception points. Conclusions The waitlist outcome calculator highlights ongoing disparities in access to liver transplant and may assist providers in understanding and counseling their patients about likely outcomes on the waiting list.

Estimated GFR and Mortality in Older Men: Are All eGFR Formulae Equal?

Background: Recently, the first estimated glomerular filtration rate (eGFR) formula specifically developed for community-dwelling older adults, the Berlin Initiative Study Equation 2 (BIS2), was reported. To date, however, no study has examined the performance of the BIS2 to predict death in older adults as compared to equations used clinically and in research. Methods: We prospectively followed 2,994 community-dwelling men (age 76.4 ± 5.6) enrolled in the MrOS Sleep Study. We calculated baseline eGFR from serum creatinine and cystatin-C using the BIS2, Chronic Kidney Disease Epidemiology (CKD-EPIcr,cysc), CKD-EPIcysc and CKD-EPIcr equations. Analyses included Cox-proportional hazards regression and net reclassification improvement (NRI) for the outcomes of all-cause and cardiovascular death. Results: Follow-up time was 7.3 ± 1.9 years. By BIS2, 42 and 11% had eGFR <60 and <45, respectively, compared to CKD-EPIcr (23 and 6%), CKD-EPIcysc (36 and 13%) and CKD-EPIcr,cysc (28 and 8%). BIS2 eGFR <45 was associated with twofold higher rate of all-cause mortality when compared to eGFR ≥75 after multivariate adjustment (HR 2.1, 95% CI 1.5-2.8). Results were similar for CKD-EPIcr,cysc <45 (HR 2.1, 95% CI 1.6-2.7) and CKD-EPIcysc <45 (HR 2.1, 95% CI 1.7-2.7) and weaker for CKD-EPIcr <45 (HR 1.5, 95% CI 1.2-2.0). In NRI analyses, when compared to CKD-EPIcr,cysc, both BIS2 and CKD-EPIcr equations more often misclassified participants with respect to mortality. We found similar results for cardiovascular death. Conclusion: The BIS2 did not outperform and the CKD-EPIcr was inferior to the cystatin C-based CKD-EPI equations to predict death in this cohort of older men. Thus, the cystatin C-based CKD-EPI equations are the formulae of choice to predict death in community-dwelling older men.

Beyond "Median Waiting Time": Development and Validation of a Competing Risk Model to Predict Outcomes on the Kidney Transplant Waiting List.

Background Median historical time to kidney transplant is misleading because it does not convey the competing risks of death or removal from the waiting list. We developed and validated a competing risk model to calculate likelihood of outcomes for kidney transplant candidates and demonstrate how this information differs from median time to transplant. Methods Data were obtained from the US Scientific Registry of Transplant Recipients. The retrospective cohort included 163 636 adults listed for kidney transplant before December 31, 2011. Predictors were age, sex, blood type, calculated panel-reactive antibodies, donation service area, dialysis duration, comorbid conditions, and body mass index. Outcomes were deceased or living donor transplant, death or removal from the list due to deteriorating medical condition, or removal due to other reasons. We calculated hazards for the possible outcomes, then the cumulative incidence function for a given candidate using competing risk methodology. Discrimination and calibration were assessed through C statistics and calibration plots for each cause-specific Cox proportional hazard model. Results C statistics ranged from 0.64 to 0.73. Calibration plots showed good calibration. The competing risk model shows probability of all possible outcomes for up to 12 years given a candidates characteristics, contrasted with the median waiting time for that candidates donation service area. Conclusions A competing risk model conveys more relevant information than the median waiting time for a given transplant center. This model will be updated to create a calculator reflecting the most recent outcomes and changes in allocation policy. It illustrates the conversations that should be initiated with transplant candidates.

Cystatin C and the Risk of Frailty and Mortality in Older Men

Background This study examines the association between cystatin C (cysC) levels and risks of progression of frailty status or death in older men. Methods Prospective study of 2,613 men without overt frailty aged 67 years and older enrolled in the MrOS ancillary sleep study. Baseline measurements included serum cysC, serum creatinine, and frailty status. Repeat frailty status, performed an average of 3.4 years later, was assessed as an ordinal outcome of robust, intermediate stage (prefrail), frail or dead. Results Mean age was 75.7 years. Men with higher cysC were older and had a higher comorbidity burden. After adjusting for age, clinical site, and race, higher cysC was associated with nearly twofold greater odds of being classified as intermediate stage versus robust (OR quartile 4 vs 1; 1.82, 95% confidence interval [CI] 1.35-2.45), a threefold greater odds of frailty versus robust (OR quartile 4 vs 1; 3.13, 95% CI 2.03-4.82), and a more than fivefold greater odds of death versus robust (OR quartile 4 vs 1; 5.48, 95% CI 2.98-10.08). Results were similar for cysC-based estimated glomerular filtration rate (eGFR). This relationship was attenuated but persisted after adjusting for additional potential confounders including baseline frailty status, body mass index, smoking status, comorbidity burden, self-reported disability, and serum albumin. In contrast, neither serum creatinine nor creatinine-based eGFR was associated in a graded manner with higher risks of development of frailty or death. Conclusions In this cohort of older men without overt frailty, higher cysC and cysC-based eGFR, but not creatinine or creatinine-based estimates of GFR, were associated with increased risks of frailty or death. These findings suggest that higher cysC level may be a promising biomarker for unsuccessful aging as manifested by increased risks of frailty and death.