Biomarkers of vascular calcification and mortality in patients with ESRD

BACKGROUND

Vascular calcification is common among patients undergoing dialysis and is associated with mortality. Factors such as osteoprotegerin (OPG), osteopontin (OPN), bone morphogenic protein-7 (BMP-7), and fetuin-A are involved in vascular calcification.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

OPG, OPN, BMP-7, and fetuin-A were measured in blood samples from 602 incident dialysis patients recruited from United States dialysis centers between 1995 and 1998 as part of the Choices for Healthy Outcomes In Caring for ESRD Study. Their association with all-cause and cardiovascular mortality were assessed using Cox proportional hazards models adjusted for demographic characteristics, comorbidity, serum phosphate, and calcium. An interaction with diabetes was tested because of its known association with vascular calcification. Predictive accuracy of selected biomarkers was explored by C-statistics in nested models with training and validation subcohorts.

RESULTS

Higher OPG and lower fetuin-A levels were associated with higher mortality over up to 13 years of follow-up (median, 3.4 years). The adjusted hazard ratios (HR) for highest versus lowest tertile were 1.49 (95% confidence interval [95% CI], 1.08 to 2.06) for OPG and 0.69 (95% CI, 0.52 to 0.92) for fetuin-A. In stratified models, the highest tertile of OPG was associated with higher mortality among patients without diabetes (HR, 2.42; 95% CI, 1.35 to 4.34), but not patients with diabetes (HR, 1.26; 95% CI, 0.82 to 1.93; P for interaction=0.001). In terms of cardiovascular mortality, higher fetuin-A was associated with lower risk (HR, 0.85 per 0.1 g/L: 95% CI, 0.75 to 0.96). In patients without diabetes, higher OPG was associated with greater risk (HR for highest versus lowest tertile, 2.91; 95% CI, 1.06 to 7.99), but not in patients with diabetes or overall. OPN and BMP-7 were not independently associated with outcomes overall. The addition of OPG and fetuin-A did not significantly improve predictive accuracy of mortality.

CONCLUSIONS

OPG and fetuin-A may be risk factors for all-cause and cardiovascular mortality in patients undergoing dialysis, but do not improve risk prediction.

Serum β-trace protein and risk of mortality in incident hemodialysis patients

BACKGROUND AND OBJECTIVES

Residual kidney function in dialysis patients is associated with better survival, but there are no simple methods for its assessment. β-Trace protein is a novel endogenous filtration marker of kidney function that is not removed during hemodialysis and may serve as a marker for residual kidney function similar to serum creatinine in patients not on dialysis. The objective of this study was to determine the association of serum β-trace protein with mortality in incident hemodialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Serum β-trace protein was measured in baseline samples from 503 participants of a national prospective cohort study of incident dialysis patients with enrollment during 1995-1998 and follow-up until 2004. Outcomes were all-cause and cardiovascular disease mortality analyzed using Cox regression adjusted for demographic, clinical, and treatment factors.

RESULTS

Serum β-trace protein levels were higher in individuals with no urine output compared with individuals with urine output (9.0±3.5 versus 7.6±3.1 mg/L; P<0.001). There were 321 deaths (159 deaths from cardiovascular disease) during follow-up (median=3.3 years). Higher β-trace protein levels were associated with higher risk of mortality. The adjusted hazard ratio and 95% confidence interval for all-cause mortality per doubling of serum β-trace protein was 1.36 (1.09-1.69). The adjusted hazard ratios (95% confidence intervals) for all-cause mortality in the middle and highest tertiles compared with the lowest tertile were 0.95 (0.69-1.32) and 1.72 (1.25-2.37). Similar results were noted for cardiovascular disease mortality.

CONCLUSIONS

The serum level of β-trace protein is an independent predictor of death and cardiovascular disease mortality in incident hemodialysis patients.

Predictors and consequences of higher estimated glomerular filtration rate at dialysis initiation

There have been no studies in pediatric dialysis patients to evaluate the impact of higher estimated glomerular filtration rate (eGFR) at dialysis initiation on clinical outcomes. Baseline clinical and demographic information was collected for children aged 1-18 years undergoing incident dialysis from 1995-2002 within the United States Renal Data System. Baseline eGFRs calculated by the Schwartz formula were categorized as high (>15 ml/min/1.73 m(2)) or low (< or = 15 ml/min/1.73 m(2)). We determined predictors of eGFR at baseline, and associations between baseline eGFR and subsequent hospitalization for hypertension (HTN) or pulmonary edema (PE) in a longitudinal nonconcurrent pediatric end-stage renal disease (ESRD) cohort. Twenty percent of children had a high eGFR at initiation. Black children were less likely to initiate dialysis with a high eGFR [adjusted odds ratio (adjOR) 0.71, p < 0.001]. Girls were less likely to have a high eGFR at baseline (adjOR 0.71, p < 0.001). Children who received predialysis erythropoietin therapy were more likely to start dialysis with a high eGFR (adjOR 6.67, p < 0.001). Children with higher baseline eGFR were found to have a 21% decreased risk of hospitalization [adjusted hazard ratio (HR) 0.79, 95% confidence interval (CI) 0.65-0.96, p = 0.02]. It is not known whether this clinical benefit will result in decreased mortality and complication rates from cardiovascular disease.

Age and comorbidities are effect modifiers of gender disparities in renal transplantation

Women have less access to kidney transplantation than men, but the contributions of age and comorbidity to this disparity are largely unknown. We conducted a national cohort study of 563,197 patients with first-onset ESRD between 2000 and 2005. We used multivariate generalized linear models to evaluate both access to transplantation (ATT), defined as either registration for the deceased-donor waiting list or receiving a live-donor transplant, and survival benefit from transplantation, defined as the relative rate of survival after transplantation compared with the rate of survival on dialysis. We compared relative risks (RRs) between women and men, stratified by age categories and the presence of common comorbidities. Overall, women had 11% less ATT than men. When the model was stratified by age, 18- to 45-yr-old women had equivalent ATT to men (RR 1.01), but with increasing age, ATT for women declined dramatically, reaching a RR of 0.41 for those who were older than 75 yr, despite equivalent survival benefits from transplantation between men and women in all age subgroups. Furthermore, ATT for women with comorbidities was lower than that for men with the same comorbidities, again despite similar survival benefits from transplantation. This study suggests that there is no disparity in ATT for women in general but rather a marked disparity in ATT for older women and women with comorbidities. These disparities exist despite similar survival benefits from transplantation for men and women regardless of age or comorbidities.

Incidence of Atherosclerotic Cardiovascular Disease Among HIV Patients Receiving Dialysis

BACKGROUND

Atherosclerotic cardiovascular disease (ASCVD) is increasing in incidence in persons with human immunodeficiency virus (HIV). It is not known whether the morbidity and mortality rate of ASCVD is similarly increasing among patients with HIV end-stage renal disease (ESRD), who are living longer since the initiation of newer therapeutic regimens in 1997.

METHODS

We conducted a population-based study of 8,312 HIV ESRD patients enrolled in the US Renal Data System from 1987 to 2001. We determined the incidence of fatal and nonfatal ASCVD events stratified by date of dialysis therapy initiation.

RESULTS

There were 3,112 HIV ESRD patients (77.9% men; mean age, 39.6 +/- 9.6 years) who initiated dialysis therapy before 1997 and 2,371 patients (71.5% men; mean age, 41.3 +/- 9.7 years) who initiated dialysis therapy after 1997. Cumulative incidences of ASCVD for those initiating dialysis therapy before 1997 compared with after 1997 were 10.6% versus 13.5% at 12 months, 18.8% versus 27.6% at 24 months, 26.2% versus 42.4% at 36 months, and 33.7% versus 65.9% at 48 months (P < 0.0001 by log rank). Those who initiated dialysis therapy after 1997 had a greater risk for developing ASCVD (adjusted hazard ratio, 1.57; 95% confidence interval, 1.29 to 1.92) than those who initiated dialysis therapy before 1997 after adjusting for demographics and ASCVD risk factors.

CONCLUSION

There is an increased risk for ASCVD in patients with HIV who initiated dialysis therapy after 1997. This may reflect the long-term complications of multidrug regimens, as well as improved survival from these regimens leading to prolonged exposure to ASCVD risk factors.