Huiling Xiao

Racial Variation in Medical Outcomes among Living Kidney Donors

BACKGROUND Data regarding health outcomes among living kidney donors are lacking, especially among nonwhite persons. METHODS We linked identifiers from the Organ Procurement and Transplantation Network (OPTN) with administrative data of a private U.S. health insurer and performed a retrospective study of 4650 persons who had been living kidney donors from October 1987 through July 2007 and who had post-donation nephrectomy benefits with this insurer at some point from 2000 through 2007. We ascertained post-nephrectomy medical diagnoses and conditions requiring medical treatment from billing claims. Cox regression analyses with left and right censoring to account for observed periods of insurance benefits were used to estimate absolute prevalence and prevalence ratios for diagnoses after nephrectomy. We then compared prevalence patterns with those in the 2005-2006 National Health and Nutrition Examination Survey (NHANES) for the general population. RESULTS Among the donors, 76.3% were white, 13.1% black, 8.2% Hispanic, and 2.4% another race or ethnic group. The median time from donation to the end of insurance benefits was 7.7 years. After kidney donation, black donors, as compared with white donors, had an increased risk of hypertension (adjusted hazard ratio, 1.52; 95% confidence interval [CI], 1.23 to 1.88), diabetes mellitus requiring drug therapy (adjusted hazard ratio, 2.31; 95% CI, 1.33 to 3.98), and chronic kidney disease (adjusted hazard ratio, 2.32; 95% CI, 1.48 to 3.62); findings were similar for Hispanic donors. The absolute prevalence of diabetes among all donors did not exceed that in the general population, but the prevalence of hypertension exceeded NHANES estimates in some subgroups. End-stage renal disease was identified in less than 1% of donors but was more common among black donors than among white donors. CONCLUSIONS As in the general U.S. population, racial disparities in medical conditions occur among living kidney donors. Increased attention to health outcomes among demographically diverse kidney donors is needed. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others.)

Bariatric surgery among kidney transplant candidates and recipients: Analysis of the United States Renal Data System and literature review

Background. Limited data exist on the safety and efficacy of bariatric surgery (BS) in patients with kidney failure. Methods. We examined Medicare billing claims within USRDS registry data (1991–2004) to identify BS cases among renal allograft candidates and recipients. Results. Of 188 BS cases, 72 were performed pre-listing, 29 on the waitlist, and 87 post-transplant. Roux-en-Y gastric bypass was the most common procedure. Thirty-day mortality after BS performed on the waitlist and post-transplant was 3.5%, and one transplant recipient lost their graft within 30 days after BS. BMI data were available for a subset and suggested median excess body weight loss of 31%–61%. Comparison to published clinical trials of BS in populations without kidney disease indicates comparable weight loss but higher post-BS mortality in the USRDS sample. Conclusions. Given the substantial contributions of obesity to excess morbidity and mortality, BS warrants prospective study as a strategy for improving outcomes before and after kidney transplantation.

Variations in the risk for cerebrovascular events after kidney transplant compared with experience on the waiting list and after graft failure.

BACKGROUND AND OBJECTIVES This study examined the risks, predictors, and mortality implications of cerebrovascular disease events after kidney transplantation in a national cohort. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This analysis used United States Renal Data System registry data to study retrospectively Medicare-insured kidney transplant candidates (n = 51,504), recipients (n = 29,614), and recipients with allograft failure (n = 2954) in 1995 through 2002. New-onset cerebrovascular disease events including ischemic stroke, hemorrhagic stroke, and transient ischemic attacks were ascertained from billing records, and participants were followed until Medicare-end or December 31, 2002. Multivariable survival analysis was used to compare cerebrovascular disease event incidence and risk profiles among the study samples. RESULTS The cumulative, 3-yr incidence of de novo cerebrovascular disease events after transplantation was 6.8% and was lower than adjusted 3-yr estimates of 11.8% on the waiting list and 11.2% after graft loss. In time-dependent regression, transplantation predicted a 34% reduction in subsequent, overall cerebrovascular disease events risk compared with remaining on the waiting list, whereas risk for cerebrovascular disease events increased >150% after graft failure. Similar relationships with transplantation and graft loss were observed for each type of cerebrovascular disease event. Smoking was a potentially preventable correlate of posttransplantation cerebrovascular disease events. Women were not protected. All forms of cerebrovascular disease event diagnoses after transplantation predicted increased mortality. CONCLUSIONS Along with known benefits for cardiac complications, transplantation with sustained graft function seems to reduce risk for vascular disease events involving the cerebral circulation.

Depression diagnoses after living kidney donation: linking U.S. Registry data and administrative claims.

Background Limited data exist on correlates of psychological outcomes after kidney donation. Methods We used a database integrating Organ Procurement and Transplantation Network registrations for 4650 living kidney donors from 1987 to 2007 with administrative data of a U.S. private health insurer (2000–2007 claims) to identify depression diagnoses among prior living donors. The burden and demographic correlates of depression after enrollment in the insurance plan were estimated by Cox regression. Graft failure and death of the donor’s recipient were examined as time-varying exposures. Results After start of insurance benefits, the cumulative frequency of depression diagnosis was 4.2% at 1 year and 11.5% at 5 years, and depression among donors was less common than among age- and gender-matched general insurance beneficiaries (rate ratio, 0.70; 95% confidence intervals [CI], 0.60–0.81). Demographic and clinical correlates of increased likelihood of depression diagnoses among the prior donors included female gender, white race, and some perioperative complications. After adjustment for donor demographic factors, recipient death (adjusted hazard ratio (aHR), 2.23; 95% CI, 1.11–4.48) and death-censored graft failure (aHR, 3.30; 95% CI, 1.49–7.34) were associated with two to three times the relative risk of subsequent depression diagnosis among nonspousal unrelated donors. There were trends toward increased depression diagnoses after recipient death and graft failure among spousal donors but no evidence of associations of these recipient events with the likelihood of depression diagnosis among related donors. Conclusions Recipient death and graft loss predict increased depression risk among unrelated living donors in this privately insured sample. Informed consent and postdonation care should consider the potential impact of recipient outcomes on the psychological health of the donor.

Incidence, Predictors, and Associated Outcomes of Atrial Fibrillation after Kidney Transplantation

The risk for and predictors of atrial fibrillation (AF) after kidney transplantation are not well described. Registry data that were collected by the United States Renal Data System were used to investigate retrospectively new-onset AF among adult first renal allograft recipients and transplant candidates who received a transplant or were wait-listed in 1995 to 2001 with Medicare as the primary payer. AF events were ascertained from billing records, and participants were followed until loss of Medicare coverage or December 31, 2001. Cox hazards analysis was used to identify independent correlates of posttransplantation AF (adjusted hazard ratio [AHR]; 95% confidence interval [CI]) and to examine AF as an outcomes predictor. Among 31,136 eligible transplant recipients, the cumulative incidence of new-onset AF was 3.6% (95% CI 3.4 to 3.8%) and 7.3% (95% CI 7.0 to 7.6%) at 12 and 36 mo and declined below the demographics-adjusted cumulative incidence on the waiting list by approximately 17 mo. Risk factors for posttransplantation AF included older recipient age, male gender, white race, renal failure from hypertension, and coronary artery disease. Extended pretransplantation dialysis duration, posttransplantation diabetes, and graft failure were identified as potentially modifiable correlates of AF. In separate analyses, AF independently predicted death (AHR 3.2; 95% CI 2.9 to 3.6) and death-censored graft loss (AHR 1.9; 95% CI 1.6 to 2.3). As the population of renal transplant recipients grows older, the incidence and prevalence of AF among these patients will likely increase. Appropriate risk stratification may identify transplant recipients who are in need of close monitoring for and management of this adverse cardiovascular event.

Early clinical complications after ABO incompatible live donor kidney transplantation: A national study of Medicare-insured recipients

Background Descriptions of the sequelae of ABO-incompatible (ABOi) kidney transplantation are limited to single-center reports, which may lack power to detect important effects. Methods We examined U.S. Renal Data System registry data to study associations of ABOi live-donor kidney transplantation with clinical complications in a national cohort. Among 14,041 Medicare-insured transplants in 2000 to 2007, 119 non–donor-A2 ABOi transplants were identified. A2-incompatible (n=35) transplants were categorized separately. Infection and hemorrhage events were identified by diagnosis codes on billing claims. Associations of ABO incompatibility with complications were assessed by multivariate Cox regression. Results Recipients of ABOi transplants experienced significantly (P<0.05) higher incidence of wound infections (12.7% vs. 7.3%), pneumonia (7.6% vs. 3.8%), and urinary tract infections (UTIs) or pyelonephritis (24.5% vs. 15.3%) in the first 90 days compared with ABO-compatible recipients. In adjusted models, ABO incompatibility was associated with twice the risk of pneumonia (adjusted hazard ratio [aHR], 2.22; 95% confidence interval [CI], 1.14–4.33) and 56% higher risk of UTIs or pyelonephritis (aHR, 1.56; 95% CI, 1.05–2.30) in the first 90 posttransplantation days, and 3.5 times the relative risk of wound infections in days 91 to 365 (aHR, 3.55; 95% CI, 1.92–6.57). ABOi recipients, 19% of whom underwent pre- or peritransplant splenectomy, experienced twice the adjusted risk of early hemorrhage (aHR, 1.96; 95% CI, 1.19–3.24). A2-incompatible transplantation was associated only with early risk of UTIs or pyelonephritis. Conclusion ABOi transplantation offers patients with potential live donors an additional transplant option but with higher risks of infectious and hemorrhagic complications. Awareness of these complications may help improve protocols for the management of ABOi transplantation.

Joint Association of Hyperuricemia and Reduced GFR on Cardiovascular Morbidity: A Historical Cohort Study Based on Laboratory and Claims Data From a National Insurance Provider

BACKGROUND Hyperuricemia is common in patients with chronic kidney disease (CKD). We assessed the relationship of increased serum uric acid levels with cardiovascular risk across levels of kidney function. STUDY DESIGN Historical cohort study. SETTING & PARTICIPANTS Study data were drawn from administrative records of a national private health insurer (2003-2006). We included all adult beneficiaries with concurrently measured serum creatinine and serum uric acid. Patients with acute kidney failure or undergoing renal replacement therapy at baseline were excluded. PREDICTORS Serum uric acid concentration and estimated glomerular filtration rate (eGFR). OUTCOMES & MEASUREMENTS Cardiovascular diagnoses (myocardial infarction, subacute coronary heart disease, heart failure, cerebrovascular disease, or peripheral arterial disease) ascertained from billing claims. Cox proportional hazard models were used to test the association of predictors with cardiovascular morbidity. Models were adjusted for sociodemographic characteristics, selected comorbid conditions, and laboratory results. RESULTS In 148,217 eligible patients, mean eGFR was 84 mL/min/1.73 m(2) and the prevalence of CKD stages 3-5 was 6.0%. Hyperuricemia (serum uric acid >7 mg/dL) was found in 15.6% of patients. The 40-month cumulative incidence of cardiovascular events (mean follow-up, 15.3 months) was 8.1%. Cardiovascular risk was associated independently with uric acid level, and this association was stronger in patients with lower eGFRs. LIMITATIONS Observational design, lack of information for mortality and potential confounders, single creatinine and uric acid assessment. CONCLUSIONS Serum uric acid concentration was an independent correlate of cardiovascular morbidity, and this association was stronger in patients with severely decreased eGFR. This investigation provides a rationale for further study of serum uric acid-lowering interventions on cardiovascular risk in the general population and patients with CKD.

Perioperative Complications after Living Kidney Donation: A National Study

We integrated the US transplant registry with administrative records from an academic hospital consortium (97 centers, 2008–2012) to identify predonation comorbidity and perioperative complications captured in diagnostic, procedure, and registry sources. Correlates (adjusted odds ratio, aOR) of perioperative complications were examined with multivariate logistic regression. Among 14 964 living kidney donors, 11.6% were African American. Nephrectomies were predominantly laparoscopic (93.8%); 2.4% were robotic and 3.7% were planned open procedures. Overall, 16.8% of donors experienced a perioperative complication, most commonly gastrointestinal (4.4%), bleeding (3.0%), respiratory (2.5%), surgical/anesthesia‐related injuries (2.4%), and “other” complications (6.6%). Major Clavien Classification of Surgical Complications grade IV or higher affected 2.5% of donors. After adjustment for demographic, clinical (including comorbidities), procedure, and center factors, African Americans had increased risk of any complication (aOR 1.26, p = 0.001) and of Clavien grade II or higher (aOR 1.39, p = 0.0002), grade III or higher (aOR 1.56, p < 0.0001), and grade IV or higher (aOR 1.56, p = 0.004) events. Other significant correlates of Clavien grade IV or higher events included obesity (aOR 1.55, p = 0.0005), predonation hematologic (aOR 2.78, p = 0.0002) and psychiatric (aOR 1.45, p = 0.04) conditions, and robotic nephrectomy (aOR 2.07, p = 0.002), while annual center volume >50 (aOR 0.55, p < 0.0001) was associated with lower risk. Complications after live donor nephrectomy vary with baseline demographic, clinical, procedure, and center factors, but the most serious complications are infrequent. Future work should examine underlying mechanisms and approaches to minimizing the risk of perioperative complications in all donors.

Renal Function and Healthcare Costs in Patients with Polycystic Kidney Disease

BACKGROUND AND OBJECTIVES Characterizing relationships of kidney function to healthcare costs in polycystic kidney disease has applications for economic evaluations of standard and emerging therapies. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS The administrative records (2003 to 2006) of a private health insurer were examined to identify polycystic kidney disease patients (n = 1913) from ICD9 diagnosis codes on billing claims. The first available diagnostic claim was assumed as an index date, and baseline estimated GFR (eGFR) was computed using closest serum creatinine value. The associations of eGFR with annualized charges were modeled by nonlinear and linear regression. RESULTS Medical, pharmacy, and total healthcare costs varied significantly by baseline kidney function, such that mean total annualized charges (unadjusted) were approximately 5-fold higher in patients with eGFR < 15 ml/min compared with those with eGFR >or= 90 ml/min. After adjustment for age and gender, total charges did not differ significantly among patients with eGFR > 30 ml/min, and but rose precipitously with eGFR < 30 ml/min. Each ml/min decline <30 ml/min predicted approximately

National assessment of early biliary complications following liver transplantation: Incidence and outcomes

5435 higher adjusted annual charges. Results were similar after adjustment for baseline diabetes and cardiovascular disease as identified in claims, while significantly higher adjusted charges were detected with eGFR = 31 to 60 ml/min versus >or=90 ml/min in a subgroup free of diabetes and cardiovascular disease. CONCLUSIONS Healthcare charges are associated with advanced renal dysfunction in polycystic kidney disease patients. Strategies that prevent loss of renal function below 30 ml/min have the potential to generate substantial reductions in medical charges.