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Comparing mortality rates on CAPD/CCPD and hemodialysis. The Canadian experience: fact or fiction?
D E Schaubel1, H I Morrison, S S Fenton
1Laboratory Centre for Disease Control, Health Canada, Ottawa.
Insights
Continuous ambulatory/cyclic peritoneal dialysis (CAPD/CCPD) shows lower mortality rates than hemodialysis (HD), especially within the first two years. This study highlights challenges in comparing dialysis modalities due to potential biases and differing methodologies.
Area of Science:
- Nephrology
- Renal Replacement Therapy
- Dialysis Modalities
Background:
- Hemodialysis (HD) and continuous ambulatory/cyclic peritoneal dialysis (CAPD/CCPD) are primary renal replacement therapies.
- Comparing mortality rates between HD and CAPD/CCPD is crucial for patient care and treatment selection.
Purpose of the Study:
- To compare mortality rates between hemodialysis (HD) and continuous ambulatory/cyclic peritoneal dialysis (CAPD/CCPD).
- To contrast findings with previous investigations and explore reasons for discrepancies in reported outcomes.
- To discuss the implications of different statistical approaches on observed mortality differences.
Main Methods:
- Utilized patient-specific data from the Canadian Organ Replacement Register for 14,483 patients initiating renal replacement therapy (RRT) between 1990 and 1995.
- Employed an "as-treated" (AT) analysis using Poisson regression to calculate mortality rate ratios (RR), adjusting for age, diagnosis, and comorbidities.
- Conducted an "intent-to-treat" (ITT) analysis using Cox regression to estimate hazard ratios (HR) based on treatment modality at day 90.
Main Results:
- The "as-treated" analysis revealed significantly lower adjusted mortality rates for CAPD/CCPD compared to HD (RR = 0.73).
- The protective effect of CAPD/CCPD was most pronounced in the initial two years following RRT initiation.
- The "intent-to-treat" analysis showed a substantially diminished effect, with a hazard ratio of 0.93 for CAPD/CCPD versus HD.
Conclusions:
- CAPD/CCPD is not inferior to HD, particularly for short-term outcomes.
- Direct comparison of mortality between CAPD/CCPD and HD is complex and prone to bias.
- Variability in study findings is attributed to differences in patient populations, study designs, statistical methods, and covariate interactions.
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.