Uyen Duong

Serum Albumin as a Predictor of Mortality in Peritoneal Dialysis: Comparisons With Hemodialysis

BACKGROUND Serum albumin level predicts mortality in dialysis patients and is used to assess their health status and the quality of delivered care. Whether the threshold level of serum albumin at which mortality risk increases in peritoneal dialysis (PD) patients is the same as for hemodialysis (HD) patients has not been studied. STUDY DESIGN Observational cohort study of dialysis patients undertaken to determine the survival-predictability of serum albumin level in PD patients and compare it with that in HD patients. SETTING & PARTICIPANTS 130,052 dialysis patients (PD, 12,171; HD, 117,851) who received treatment in any of the 580 dialysis units owned by DaVita Inc between July 1, 2001, through June 30, 2006, followed up through June 30, 2007. PREDICTOR Baseline and time-averaged serum albumin level (assayed using bromcresol green) and change in serum albumin level over 6 months. OUTCOME MEASURES All-cause, cardiovascular, and infection-related mortality. RESULTS PD patients with baseline serum albumin level <3.0 g/dL had a more than 3-fold higher adjusted risk of all-cause and cardiovascular mortality and 3.4-fold higher risk of infection-related mortality (reference group: serum albumin, 4.00-4.19 g/dL). Adjusted all-cause mortality was significantly lower in PD patients with a ≥0.3-g/dL increase in serum albumin level over 6 months and significantly higher in those for whom it decreased by ≥0.2 g/dL (reference group: serum albumin change, +0.1 to -0.1 g/dL). A significant increase in death risk was evident for HD patients with serum albumin level <4.0 g/dL, but at <3.8 g/dL for PD patients. For each albumin category, overall death risk for PD patients was lower than for HD patients (reference group: HD patients with serum albumin of 4.00-4.19 g/dL). LIMITATIONS Study can identify associations only without attribution of causality and residual confounding cannot be excluded. CONCLUSIONS Serum albumin predicts all-cause, cardiovascular, and infection-related mortality in both PD and HD patients. However, the threshold at which risk of death increases varies by dialysis modality, and this difference should be considered by agencies or organizations that set quality standards.

Glycemic Control and Survival in Peritoneal Dialysis Patients with Diabetes Mellitus

BACKGROUND AND OBJECTIVES The optimal target for glycemic control has not been established for diabetic peritoneal dialysis (PD) patients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We examined mortality-predictability of hemoglobin A1c random serum glucose in a contemporary cohort of diabetic PD patients treated in DaVita dialysis clinics July 2001 through June 2006 with follow-up through June 2007. RESULTS We identified 2798 diabetic PD patients with A1c data. Serum glucose correlated with A1C (r=0.51). Adjusted all-cause death hazard ratio and 95% confidence interval for baseline A1c increments of 7.0 to 7.9%, 8.0 to 8.9%, 9.0 to 9.9%, and ≥10%, compared with 6.0 to 6.9% (reference), were 1.13 (0.97 to 1.32), 1.05 (0.88 to 1.27), 1.06 (0.84 to 1.34), and 1.48 (1.18 to 1.86); and for time-averaged A1c values were 1.10 (0.96 to 1.27), 1.28 (1.07 to 1.53), 1.34 (1.05 to 1.70), and 1.81 (1.33 to 2.46), respectively. The A1c-mortality association was modified by hemoglobin level such that higher all-cause mortality was evident only in nonanemic patients. Similar but non-significant trends in cardiovascular death risk was found across A1c increments. Adjusted all-cause death HR for time-averaged blood glucose 150 to 199, 200 to 249, 250 to 299, and ≥300 mg/dl, compared with 60 to 99 mg/dl (reference), were 1.02 (0.70 to 1.47), 1.12 (0.77 to 1.63), 1.45 (0.97 to 2.18), and 2.10 (1.37 to 3.20), respectively. CONCLUSIONS Poor glycemic control appears associated incrementally with higher mortality in PD patients. Moderate to severe hyperglycemia is associated with higher death risk especially in certain subgroups.

Ownership patterns of dialysis units and peritoneal dialysis in the United States: utilization and outcomes.

BACKGROUND Peritoneal dialysis (PD) provides outcomes similar to hemodialysis, but its use has decreased in the United States despite its potential for substantial taxpayer savings. We undertook this study to determine the relationship between dialysis unit ownership with PD use and outcomes. STUDY DESIGN Observational study. SETTING & PARTICIPANTS All incident dialysis patients (1996 to 2004) from the US Renal Data System. PREDICTOR Large dialysis organization (LDO), defined as corporations owning 20 or more freestanding dialysis units located in more than 1 state. OUTCOMES & MEASUREMENTS Odds for an incident dialysis patient undergoing PD and hazards for death on follow-up in incident PD patients for each of the 5 LDOs (non-LDO as reference). RESULTS During the 9-year period, 785,531 patients started maintenance dialysis therapy; the proportion receiving care in LDOs increased from 39% to 63%. There were consistent differences in PD use. It was significantly lower in LDO 2 (adjusted odds ratio [OR], 0.66; 95% confidence interval [CI], 0.64 to 0.68), LDO 3 (OR, 0.82; 95% CI, 0.80 to 0.85), and LDO 4 (OR, 0.96; 95% CI, 0.92 to 0.995) and higher in LDO 1 (adjusted OR, 1.06; 95% CI, 1.02 to 1.11) and LDO 5 (adjusted OR, 1.09; 95% CI, 1.06 to 1.12). Between 2000 and 2004, LDO 2 had the least use and greatest risk of death (hazard ratio, 1.08; 95% CI, 1.02 to 1.14); LDO 1 had greater use and the lowest death risk (hazard ratio, 0.87; 95% CI, 0.78 to 0.96). LIMITATIONS Only cross-sectional associations can be described. CONCLUSIONS Three of the 5 LDOs had consistently lower PD use. Patients treated in the LDO with the lowest use of PD had the greatest risk of death. Understanding relationships among providers, physicians, and dialysis modality use may help devise strategies for increasing PD use in appropriate patients. This has the potential to reduce the cost of renal replacement therapy and further improve outcomes.

Association of serum alkaline phosphatase and bone mineral density in maintenance hemodialysis patients.

Recent studies indicate that serum alkaline phosphatase (AlkPhos), a surrogate of high turnover bone disease, is associated with coronary artery calcification and death risk in maintenance hemodialysis (MHD) patients. The association between AlkPhos and bone mineral density (BMD) is not well studied. We studied the association between AlkPhos and dual‐energy X‐ray absorptiometry‐assessed BMD in a group of MHD patients in Southern California. In 154 MHD patients, aged 55.3 ± 13.6 years, including 42% women, 38% Hispanics, 42% African Americans, and 55% diabetics, the mean serum AlkPhos was 121 ± 63 U/L (median: 101, Q25–75: 81–141); 36% had AlkPhos≥120 U/L and 50% had a total T‐score≤−1. Whereas the total BMD did not correlate with age (r=0.01, P=0.99) or body mass index (r=0.10, P=0.22), it correlated negatively with AlkPhos (r=−0.25, P=0.002), including after multivariate adjustment (r=−0.24, P=0.003). The proportion of patients with a high coronary artery calcification score>400 was incrementally higher across worsening BMD tertiles (P trend=0.04). The BMD was significantly worse in MHD patients with serum AlkPhos≥120 U/L compared with <120 U/L (1.01 ± 0.016 vs. 1.08 ± 0.013 g/cm2, respectively, P<0.001). The multivariate adjusted odds ratio of AlkPhos≥120 U/L for having a total T‐score<−1.0 was 2.3 (1.1–4.8, P=0.037). Among routine clinical and biochemical markers, serum AlkPhos≥120 U/L was a better predictor of total T‐score≤−1 in MHD patients. An association exists between higher serum AlkPhos and worse dual‐energy X‐ray absorptiometry‐assessed BMD in MHD patients. Given these findings, studies are indicated to examine whether interventions that lower serum AlkPhos improve BMD in MHD patients.

Dialysis modality and outcomes in kidney transplant recipients

BACKGROUND AND OBJECTIVES The influence of pretransplant dialysis modality on post-transplant outcomes is not clear. This study examined associations of pretransplant dialysis modality with post-transplant outcomes in a large national cohort of kidney transplant recipients. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Linking the 5-year patient data of a large dialysis organization to the Scientific Registry of Transplant Recipients, 12,416 hemodialysis and 2092 peritoneal dialysis patients who underwent first kidney transplantation were identified. Mortality or graft failure and delayed graft function risks were estimated by Cox regression (hazard ratio) and logistic regression (odds ratio), respectively. RESULTS Recipients treated with peritoneal dialysis pretransplantation had lower (21.9/1000 patient-years [95% confidence interval: 18.1-26.5]) crude all-cause mortality rate than those recipients treated with hemodialysis (32.8/1000 patient-years [30.8-35.0]). Pretransplant peritoneal dialysis use was associated with 43% lower adjusted all-cause and 66% lower cardiovascular death. Furthermore, pretransplant peritoneal dialysis use was associated with 17% and 36% lower unadjusted death-censored graft failure and delayed graft function risk, respectively. However, after additional adjustment for relevant covariates, pretransplant peritoneal dialysis modality was not a significant predictor of death-censored graft failure delayed graft function, respectively. Similar trends were noted on analyses using a propensity score matched cohort of 2092 pairs of patients. CONCLUSIONS Compared with hemodialysis, patients treated with peritoneal dialysis before transplantation had lower mortality but similar graft loss or delayed graft function. Confounding by residual selection bias cannot be ruled out.

Mortality Associated with Dose Response of Erythropoiesis-Stimulating Agents in Hemodialysis versus Peritoneal Dialysis Patients

Background: Several studies have shown an association between erythropoietin-stimulating agent (ESA) responsiveness and mortality in chronic kidney disease (CKD) patients. In our present study, we examined the association between prescribed ESA dose and mortality in peritoneal dialysis (PD) and hemodialysis (HD) patients. We hypothesized that PD patients received lower ESA dose for the same achieved hemoglobin compared to HD patients and that ESA dose-mortality associations were different between PD and HD patients. Methods: We compared the prescribed doses of ESA between 139,103 HD and 10,527 PD patients treated in DaVita dialysis clinics from 7/2001 through 6/2006 using adjusted Poisson regression and examined mortality-predictability of prescribed ESA dose and ESA responsiveness index (ESA/hemoglobin) in PD and HD with follow-up through 6/2007 using Cox regression models. Results: Poisson adjusted ratio of ESA dose of HD to PD was 3.6 (95% CI 3.5–3.7). In PD patients, adjusted all-cause death hazard ratios (HR) for ESA doses of 3,000–5,999, 6,000–8,999 and ≧9,000 U/week (reference <3,000 U/week) were 0.97 (0.87–1.07), 0.85 (0.76–0.95) and 1.08 (0.98–1.18), respectively; whereas in HD patients across commensurate ESA dose increments of 10,000–19,999, 20,000–29,999 and ≧30,000 U/week (reference <10,000 U/week) were 1.14 (1.11–1.17), 1.54 (1.50–1.58) and 2.15 (2.10–2.21), respectively. In PD and HD patients, the adjusted death HR of the 4th to 1st quartile of ESA responsiveness index were 1.14 (1.04–1.26) and 2.37 (2.31–2.43), respectively. Conclusions: Between 2001 and 2006, most PD patients received substantially lower ESA dose for same achieved hemoglobin levels, and low ESA responsiveness was associated with higher mortality in both HD and PD patients.

Relationship of body size and initial dialysis modality on subsequent transplantation, mortality and weight gain of ESRD patients

BACKGROUND Whether peritoneal dialysis (PD) treatment leads to greater weight gain than with hemodialysis (HD) and if this limits access of obese end-stage renal disease patients to renal transplantation has not been examined. We undertook this study to determine the interrelationship between body size and initial dialysis modality on transplantation, mortality and weight gain. METHODS Time to transplantation, time to death and weight gain were estimated in a 1:1 propensity score-matched cohort of incident HD and PD patients treated in facilities owned by DaVita Inc. between 1 July 2001 through 30 June 2006 followed through 30 June 2007 (4008 pairs) in four strata of body mass index (BMI) (<18.5, 18.5-24.99, 25.00-29.99 and ≥ 30 kg/m(2)). RESULTS Transplantation was significantly more likely in PD patients [adjusted hazards ratio (aHR) 1.48, 95% confidence interval (95% CI) 1.29-1.70]; the probability of receiving a kidney transplant was significantly higher in each strata of BMI >18.5 kg/m(2), including with BMI ≥ 30 kg/m(2) (aHR 1.45, 95% CI 1.11-1.89). PD patients had significantly lower all-cause mortality for patients with BMI 18.50-29.99 kg/m(2). Both these findings were confirmed on analyses of the entire unmatched incident cohort (PD 4008; HD 58 471). The effect of dialysis modality on weight gain was tested in 687 propensity score-matched pairs; the odds of >2, >5 or >10% weight gain were significantly lower in PD patients. CONCLUSION Treatment with PD is less likely to be associated with a significant weight gain and does not limit the access of obese patients to renal transplantation.

Association of Hemoglobin and Survival in Peritoneal Dialysis Patients

BACKGROUND AND OBJECTIVES Interventional trials and some observational studies show target hemoglobin >13 g/dl to be associated with higher mortality in erythropoiesis-stimulating agent-treated (ESA-treated) hemodialysis patients; data for peritoneal dialysis (PD) patients are limited. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We tested our hypothesis that higher and lower achieved hemoglobin levels are associated with increased mortality in 9269 ESA-treated PD patients from all DaVita dialysis clinics during the time period July 2001 through June 2006 followed through June 2007 using a time-dependent analysis. RESULTS Lower hemoglobin was associated with significantly higher all-cause mortality in ESA-treated PD patients: with hemoglobin of 11.0 to <12.0 g/dl as reference, the time-dependent adjusted death hazard ratios for hemoglobin levels of 10.0 to <11.0, 9.0 to <10.0, and ≤9.0 g/dl were 1.12 (1.00 to 1.24), 1.30 (1.12 to 1.50), and 1.38 (1.14 to 1.67), respectively. The time-dependent adjusted hazard ratios for cardiovascular death with hemoglobin levels of 10.0 to <11.0, 9.0 to <10.0, and ≤9.0 g/dl were 1.11 (0.93 to 1.32), 1.37 (1.09 to 1.72), and 1.12 (0.79 to 1.57), respectively. The same trend for association of lower hemoglobin level with higher mortality was seen in African-American and non-African American men and women. In contrast, there was no association between higher achieved hemoglobin and all-cause or cardiovascular mortality in ESA-treated PD patients. CONCLUSIONS Lower, but not higher, achieved hemoglobin is associated with higher mortality in ESA-treated PD patients. Randomized controlled trials are needed to examine the target hemoglobin level with lowest mortality in PD patients.