Biomedical subjects

D E Schaubel

Publications and source records attributed to D E Schaubel.

15 recordsLinked to original sources

PubMed2006

Mortality after kidney transplantation: a comparison between the United States and Canada.

There is a paucity of comparative studies on country-specific outcomes in kidney transplantation. We compared post-transplant mortality among primary, adult, solitary kidney transplant recipients (KTR) from the United States (n = 70 708) and Canada (n = 5773), between January 1, 1991 and December 31, 1998, using data from the Scientific Registry of Transplant Recipients and the Canadian Organ Replacement Register. Multivariable Cox regression revealed higher adjusted post-transplant mortality among U.S. (vs. Canadian) KTR (HR = 1.35 [95% CI 1.24, 1.47; p < 0.005]). Mortality risk in the first post-transplant year was similar in both countries but higher in the United States beyond the first year (HR = 1.49-1.53; p < 0.005). There was no difference in mortality among patients transplanted within 1 year of starting dialysis, but mortality was increased in U.S. (vs. Canadian) patients after 1-2 and 4+ years on dialysis (HR = 1.36-1.66; p < 0.005). Greater mortality was also seen in U.S. patients with diabetes mellitus and/or graft failure. In conclusion, there are considerable differences in the survival of KTR in the United States and Canada. A detailed examination of factors contributing to this variation may yield important insights into improving outcomes for all KTR.

Adolescent↗

PubMed2006

Liver and intestine transplantation in the United States, 1995-2004.

Three years of survival data are now available and the impact of the model for end-stage liver disease (MELD) allocation system is becoming clear. After a decline in new registrants to the waiting list in 2002, the number increased to 10 856 new patients in 2004. Since the implementation of MELD, the percentage of patients who have been on the list for 1-2 years has declined from 24% to 19%. There has been a shift upward in the percentage of patients with higher MELD scores on the waiting list. An increasing percentage of adult living donor liver recipients are over the age of 50 years; from 1% in 1997 to 51% in 2004. Parents donating to children (93% of living donors in 1995), represented only 14% in 2004. Long-term adjusted patient survival declined with increasing recipient age in adults following either DDLT or LDLT. Cirrhosis caused by chronic hepatitis C virus (HCV) is the leading indication for liver transplantation and is associated with reduced long-term survival in recipients with HCV compared to those without HCV, 68% at 5 years compared to 76%. Although the intestine waiting list has more than doubled over the last decade, an increasing number of centers now perform intestinal transplantation with greater success.

Adolescent↗

PubMed2006

Analytical methods and database design: implications for transplant researchers, 2005.

Understanding how transplant data are collected is crucial to understanding how the data can be used. The collection and use of Organ Procurement and Transplantation Network/Scientific Registry of Transplant Recipients (OPTN/SRTR) data continues to evolve, leading to improvements in data quality, timeliness and scope while reducing the data collection burden. Additional ascertainment of outcomes completes and validates existing data, although caveats remain for researchers. We also consider analytical issues related to cohort choice, timing of data submission, and transplant center variations in follow-up data. All of these points should be carefully considered when choosing cohorts and data sources for analysis. The second part of the article describes some of the statistical methods for outcome analysis employed by the SRTR. Issues of cohort and follow-up period selection lead into a discussion of outcome definitions, event ascertainment, censoring and covariate adjustment. We describe methods for computing unadjusted mortality rates and survival probabilities, and estimating covariate effects through regression modeling. The article concludes with a description of simulated allocation modeling, developed by the SRTR for comparing outcomes of proposed changes to national organ allocation policies.

Data Collection↗

PubMed2001

Effect of renal center characteristics on mortality and technique failure on peritoneal dialysis.

BACKGROUND: Recent studies report decreased mortality in patients on peritoneal dialysis (PD) over time, suggesting that advances in PD have resulted in improved patient outcomes. Our investigation sought to assess the effect of renal center characteristics on mortality and technique failure (TF) rates. METHODS: Covariates of interest included center-specific cumulative number of PD patients treated, percentage of patients who initiated dialysis on PD, and academic status. Using data obtained from the Canadian Organ Replacement Register, the 17,900 patients who received PD during the 1981 to 1997 period were studied. Mortality and TF rate ratios (RR) were estimated using Poisson regression, adjusting for age, gender, race, primary renal diagnosis, province, follow-up time, and type of PD. RESULTS: As the cumulative number of PD patients treated increased, covariate-adjusted mortality significantly decreased (P < 0.05); a weaker yet significant association was observed between number of PD patients treated and TF. As the percentage of patients initiating dialysis on PD increased, TF rates decreased significantly. No association was observed between center academic status and PD mortality or TF rates. CONCLUSIONS: These results imply that a center's experience with and degree of specialization toward PD impact strongly on PD outcomes. One hypothesis is that a center's propensity to exploit technical and non-technical advances in PD increases directly with these variables. It is also possible that, through experience, centers become more adept at identifying appropriate patients to receive PD. More detailed research is required to evaluate these hypotheses.

Academic Medical Centers↗

PubMed1999

End-stage renal disease in Canada: prevalence projections to 2005.

BACKGROUND: The incidence and prevalence of end-stage renal disease (ESRD) have increased greatly in Canada over the last 2 decades. Because of the high cost of therapy, predicting numbers of patients who will require dialysis and transplantation is necessary for nephrologists and health care planners. METHODS: The authors projected ESRD incidence rates and therapy-specific prevalence by province to the year 2005 using 1981-1996 data obtained from the Canadian Organ Replacement Register. The model incorporated Poisson regression to project incidence rates, and a Markov model for patient follow-up. RESULTS: Continued large increases in ESRD incidence and prevalence were projected, particularly among people with diabetes mellitus. As of Dec. 31, 1996, there were 17,807 patients receiving renal replacement therapy in Canada. This number was projected to climb to 32,952 by the end of 2005, for a relative increase of 85% and a mean annual increase of 5.8%. The increased prevalence was projected to be greatest for peritoneal dialysis (6.0% annually), followed by hemodialysis (5.9%) and functioning kidney transplant (5.7%). The projected annual increases in prevalence by province ranged from 4.4%, in Saskatchewan, to 7.5%, in Alberta. INTERPRETATION: The projected increases are plausible when one considers that the incidence of ESRD per million population in the United States and other countries far exceeds that in Canada. The authors predict a continued and increasing short-fall in resources to accommodate the expected increased in ESRD prevalence.

Adult↗

PubMed1999

Peritoneal dialysis reduces the use of non native fistula access in dialysis programs.

Access problems remain the major difficulty associated with chronic hemodialysis. Despite recent recommendations by the Dialysis Outcomes Quality Initiative (DOQI) that native arteriovenous (AV) fistulae are the optimal form of vascular access, grafts and central catheters are used by many patients. We analyzed our large Canadian regional dialysis program, which has a high prevalence of peritoneal dialysis, to examine the effect of dialysis modality choice on vascular access utilization. Point prevalence data were collected from our program in October 1997, and technique and patient survival data for the period 1990-1996 were analyzed and compared to data for the remainder of Canada from the Canadian Organ Replacement Register. Mortality rate ratios were estimated using a Poisson regression model to correct for comorbidity, age, and end-stage renal disease etiology. Of 141 in-center hemodialysis patients, 91 had an AV fistula, 1 had a polytetrafluoroethylene (PTFE) graft, and 49 were catheter-dependent. The program also included 20 home hemodialysis patients with AV fistulae, and 156 patients on peritoneal dialysis. No mortality risk differences between hemodialysis and peritoneal dialysis are seen in our center, nor are they seen for each modality in comparison with the remainder of Canada. Technique survival for peritoneal dialysis at our center was about 80% at 2 years, significantly greater than for Canada. For the program as a whole, 49% of patients used peritoneal dialysis 35% a native AV fistula, and 15% a central catheter. For Canada and the U.S.A. respectively, the comparable data were: peritoneal dialysis, 32% and 17%; native fistula, 33% and 15%; PTFE, 19% and 41%; and central catheter 16% and 27%. These data suggest that the use of peritoneal dialysis may allow reduced use of non native AV fistula access without mortality penalty.

Aged↗

PubMed1998

End-stage renal disease projections for Canada to 2005 using Poisson and Markov models.

BACKGROUND: End-stage renal disease (ESRD) incidence and prevalence are increasing in many countries worldwide. Due to the high cost of therapy, predicting future numbers of patients requiring dialysis and transplantation is necessary for health care planners. Projecting therapy-specific chronic disease prevalence is inherently problematic, and examples of suitable models and their application are sparse. When applied, rarely was the adequacy of such models evaluated. METHODS: We describe and illustrate a method for projecting therapy-specific ESRD prevalence in Canada for 1995-2005 using data obtained from the Canadian Organ Replacement Register. The projections combine the Poisson model for incidence rates and a Markov model for patient follow-up. Model adequacy is empirically validated by data-splitting. RESULTS: Large increases in ESRD prevalence are expected in Canada, with an average annual increase of 6.9% projected for 1995-2005. Upon validation, the projection model based on 1981-1987 data was able to predict 1994 prevalence within 1%, while projected therapy-specific prevalences closely approximated those observed. CONCLUSIONS: Therapy-specific ESRD prevalence was successfully projected using Poisson and Markov models. Where multistate prevalence forecasts are required, the method could be augmented for application to various other chronic diseases.

Adult↗

PubMed1998

Radon-progeny exposure and lung cancer risk in a cohort of Newfoundland fluorspar miners.

Although radon is a well-established lung carcinogen, there are uncertainties concerning the exposure-response relationship, whether exposures in early life are particularly hazardous, and how smoking affects the risks associated with radon exposure. A cohort study of the mortality experience of 1,743 underground fluorspar miners and 321 surface workers from 1950 to 1984 reported previously has been extended to include 6 additional years of follow-up (1985-1990). A statistically significant relationship was noted between radon-progeny exposure and risk of lung cancer mortality. Our analysis found no effect for age at first exposure. Attained age was strongly predictive of excess relative risk (ERR) per working level month (WLM) of radon exposure, falling from 0.025 for those aged less than 50 years to 0.002 for those 70 years or older. An inverse exposure-rate effect was also observed, wherein for equal total exposure, a high exposure rate (and short duration) is less harmful than a low exposure rate (and long duration). The ERR/WLM increased from 0.0019 for exposures of less than 10 years to 0.0076 for exposures of 20 or more years. The analysis of time-since-exposure windows revealed a greater ERR/WLM for exposures received in more recent periods, similar to the result for time since last exposure. Excess relative risks per WLM were higher for current smokers than for nonsmokers (never and former smokers). Analyses were consistent with a multiplicative relationship between radon-progeny exposure and current smoking and the risk of lung cancer. The assessment of radon exposure and lung cancer risk should incorporate the effects of exposure rate, time since exposure, smoking status and attained age.

Adult↗

PubMed1998

Physical activity, physical fitness, and risk of dying.

We examined the relation between physical activity, physical fitness, and all-cause mortality in a national population-based study of Canadians. We followed men and women ages 20-69 years who had participated in the Canada Fitness Survey between 1981 and 1988. We assessed risk factors for 6,246 men and 8,196 women using multivariate Poisson regression analysis. At baseline, all subjects were asymptomatic according to self-reported screening questions for cardiovascular disease. Men who expended > or =0.5 kilocalories per kilogram of body weight per day (KKD) experienced a 20% decline in risk of mortality [rate ratio (RR) = 0.82; 95% confidence interval (CI) = 0.65-1.04] when compared with subjects expending <0.5 KKD. We observed a 30% decline in risk of mortality among women expending > or =3.0 KKD relative to those expending <0.5 KKD (RR = 0.71; 95% CI = 0.45-1.11). Similar patterns of risk were evident for both men and women when analyses were restricted to participation in nonvigorous activities. Those who perceived themselves to be of less than average fitness were at increased risk of mortality (male RR = 1.64, 95% CI = 1.21-2.22; female RR = 1.66, 95% CI = 1.21-2.26). Subjects with undesirable cardiorespiratory fitness levels were more likely to die, compared with those having recommended fitness levels (RR = 1.52; 95% CI = 0.72-3.18). Fifty-three per cent of men and 35% of women reported participating in a vigorous activity. The relation between daily energy expenditure and risk of mortality in these subjects could not be evaluated, as there were few deaths. Nonetheless, our results among participants reporting no vigorous activities support the hypothesis that there is a reduction in mortality risk associated with even modest participation in activities of low intensity.

Adult↗

PubMed1997

Hemodialysis versus peritoneal dialysis: a comparison of adjusted mortality rates.

Although kidney transplantation is the preferred treatment method for patients with ESRD, most patients are placed on dialysis either while awaiting transplantation or as their only therapy. The question of which dialytic method provides the best patient survival remains unresolved. Survival analyses comparing hemodialysis and continuous ambulatory peritoneal dialysis/continuous cyclic peritoneal dialysis (CAPD/CCPD), a newer and less costly dialytic modality, have yielded conflicting results. Using data obtained from the Canadian Organ Replacement Register, we compared mortality rates between hemodialysis and CAPD/CCPD among 11,970 ESRD patients who initiated treatment between 1990 and 1994 and were followed-up for a maximum of 5 years. Factors controlled for include age, primary renal diagnosis, center size, and predialysis comorbid conditions. The mortality rate ratio (RR) for CAPD/CCPD relative to hemodialysis, as estimated by Poisson regression, was 0.73 (95% confidence interval: 0.68 to 0.78). No such relationship was found when an intent-to-treat Cox regression model was fit. Decreased covariable-adjusted mortality for CAPD/CCPD held within all subgroups defined by age and diabetes status, although the RRs increased with age and diabetes prevalence. The increased mortality on hemodialysis compared with CAPD/CCPD was concentrated in the first 2 years of follow-up. Although continuous peritoneal dialysis was associated with significantly lower mortality rates relative to hemodialysis after adjusting for known prognostic factors, the potential impact of unmeasured patient characteristics must be considered. Notwithstanding, we present evidence that CAPD/CCPD, a newer and less costly method of renal replacement therapy, is not associated with increased mortality rates relative to hemodialysis.

Adolescent↗

PubMed1997

The Canadian Organ Replacement Register on renal replacement therapy.

This report describes the demography, clinical characteristics, and outcomes for patients receiving renal replacement therapy (RRT) in Canada. Results are based on registered patients initiating RRT during the 1981-85 period using data obtained from the Canadian Organ Replacement Register (CORR).

Canada↗

PubMedDate not supplied

Sex inequality in kidney transplantation rates.

BACKGROUND: Men in the United States undergoing renal replacement therapy are more likely than women to receive a kidney transplant. However, the ability to pay may, in part, be responsible for this finding. OBJECTIVE: To compare adult male and female transplantation rates in a setting in which equal access to medical treatment is assumed. METHODS: Using data from the Canadian Organ Replacement Register, the rate of first transplantations was computed for the 20, 131 men and the 13,458 women aged 20 years or older who initiated renal replacement therapy between January 1, 1981, and December 31, 1996. Poisson regression analysis was used to estimate the male-female transplantation rate ratio, adjusting for age, race, province, calendar period, underlying disease leading to renal failure, and dialytic modality. Actuarial survival methods were used to compare transplantation probability for covariable-matched cohorts of men and women. RESULTS: Men experienced 20% greater covariable-adjusted kidney transplantation rates relative to women (rate ratio, 1.20; 95% confidence interval, 1.13-1.27). The sex disparity was stronger for cadaveric transplants (rate ratio, 1.23) compared with those from living donors (rate ratio, 1.10). The 5-year probability of receiving a transplant was 47% for men and 39% for women within covariable-matched cohorts (P<.001). The sex disparity in transplantation rates increased with increasing age. The sex effect was weaker among whites and Oriental persons (Chinese, Japanese, Vietnamese, Cambodian, Laotian, Filipino, Malaysian, Indonesian, and Korean) and stronger among blacks, Asian Indians (Indian, Pakistani, and Sri Lankan), and North American Indians (aboriginal). CONCLUSION: Since survival probability and quality of life are superior for patients who undergo transplantation relative to those who undergo dialysis, an increased effort should be made to distribute kidneys available for transplantation more equitably by sex among patients undergoing renal replacement therapy.

Actuarial Analysis↗

PubMedDate not supplied

The effect of small solute clearances on survival of anuric peritoneal dialysis patients.

OBJECTIVE: Primarily, to determine whether peritoneal small solute clearance is related to patient and technique survival among anuric peritoneal dialysis [continuous ambulatory (CAPD) and automated peritoneal dialysis (APD)] patients. A secondary goal was to describe the ability to attain Dialysis Outcomes Quality Initiative (DOQI) targets among anuric patients on peritoneal dialysis. DESIGN: Retrospective cohort study via chart reviews. SETTING: Peritoneal Dialysis Unit of Toronto Hospital (Western Division). PATIENTS: The study included 122 CAPD and APD patients between January 1992 and September 1997, with 24-hour urine volume less than 100 mL, or renal creatinine clearance (CCr) less than 1 mL/minute. Adequacy data were available for 115 patients. OUTCOME MEASURES: Mortality and technique failure (TF). Regression analysis was used to estimate the mortality and TF rate ratios (RR) for peritoneal Kt/V urea (pKt/V) and pCCr, adjusting for age, gender, diabetes, months of follow-up prior to anuria, albumin, transport status, coronary artery disease, cardiovascular disease, and peripheral vascular disease. RESULTS: Fifty seven per cent (51/89) of patients on CAPD and 81% (21/26) on APD had a weekly pKt/V > or = 2 and > or = 2.2, respectively (DOQI targets); whereas only 35% on CAPD (31/89) and 35% (9/26) on APD had a weekly pCCr > or = 60 U1.73 m2 and 66 L/1.73 m2, respectively. Median follow-up times among patients were 16.5 and 19.5 months pre- and postanuria, respectively. Patients with pKt/V > or = 1.85 experienced a strong decrease in patient mortality (RR = 0.54, p= 0.10); the effect was less pronounced for pCCr > or = 50 L/1.73 m2 (RR = 0.63, p = 0.25). No relationship was observed between pKt/V or pCCr and TF. CONCLUSION: Mortality was noticeably less frequent among patients with a pKt/V > or = 1.85 compared with those with a Kt/W < 1.85 (p = 0.10). Given the magnitude of the association, the failure to observe statistical significance relates to the size of the patient cohort. Our results imply that it is, in fact, possible to achieve DOQI targets among anuric patients on peritoneal dialysis.

Anuria↗

PubMedDate not supplied

Trends in CAPD technique failure: Canada, 1981-1997.

OBJECTIVE: Although important enhancements to continuous ambulatory peritoneal dialysis (CAPD) have occurred since its inception, few studies have explicitly evaluated trends over time in CAPD technique failure rates. To assist in quantifying the net benefit of improvements to CAPD for patient outcomes, we examined trends in technique failure rates among Canadian CAPD patients. PATIENTS: Patients initiating renal replacement therapy on CAPD (n = 7110) between 1981 and 1997. MAIN OUTCOME MEASURES: Technique failure (i.e., switch to hemodialysis). RESULTS: Total follow-up was 12,831 patient-years (pt-yr). There were 1976 technique failures, for a crude CAPD failure rate of 154.0/1000 pt-yr. Technique failure rate ratios (RR) estimated using Poisson regression and adjusted for age, gender, race, province, primary renal diagnosis, and follow-up time, were significantly reduced for the 1990-93 [RR = 0.75, 95% confidence interval (CI) = (0.68, 0.83)], 1994-95 [RR = 0.83, CI (0.75, 0.93)], and 1996-97 [RR = 0.78, CI (0.70, 0.87)] calendar periods relative to 1981-89 (RR = 1, reference). Among cause-specific technique failure rates, the greatest improvement was observed for peritonitis-attributable technique failure, with RR = 0.46, CI (0.41, 0.50) for 1990-97 relative to 1981-89. However, rates of technique failure due to inadequate dialysis were significantly elevated for the 1990-97 period [RR = 1.68, CI (1.44, 1.96)]. CONCLUSIONS: The collection of more detailed data on practice patterns would enable future studies to elucidate the cause-and-effect relationship between CAPD descriptors and technique failure, and hence assist in clinical decision-making.

Adolescent↗

PubMedDate not supplied

Comparing mortality rates on CAPD/CCPD and hemodialysis. The Canadian experience: fact or fiction?

OBJECTIVE: To compare mortality rates on hemodialysis (HD) to rates on continuous ambulatory/cyclic peritoneal dialysis (CAPD/CCPD), to contrast our results with those of other recent investigations, and to discuss reasons for discrepancies. DATA SOURCES: Patient-specific data obtained from the Canadian Organ Replacement Register on patients initiating renal replacement therapy (RRT) between 1 January 1990 and 31 December 1995 (n = 14 483). Recent mortality comparisons of CAPD and HD. MAIN OUTCOME MEASURES: Mortality rate ratio (RR) based on "as-treated" (AT) analysis incorporating treatment modality switches and adjusting for age, primary renal diagnosis, and comorbid conditions using Poisson regression. Hazard ratios (HR) were estimated using Cox regression and based on an "intent-to-treat" (ITT) analysis wherein patients were classified based on dialytic modality received on follow-up day 90. RESULTS: Adjusted mortality rates were significantly decreased on CAPD/CCPD relative to HD [RR = 0.73, 95% confidence interval (CI) = (0.69, 0.77)] based on the AT analysis. Most of the protective effect of CAPD/CCPD was concentrated in the first 2 years of follow-up post-RRT initiation. Based on the ITT analysis, the estimated CAPD/ CCPD effect was greatly reduced, with HR = 0.93 (0.87, 0.99). CONCLUSIONS: We provide further evidence that CAPD/CCPD is not an inferior dialytic modality to HD, particularly in the short term. Comparing mortality rates on CAPD/CCPD and HD is inherently difficult due to the potential for bias. Discrepancies between our results and those of previous investigations, and variability in findings among previous studies, relate to differences in clinical and demographic setting, patient populations, study design, statistical methods, and interaction between the dialytic modality effect and various other covariables.

Canada↗