Towards a Peritoneal Dialysis-First Policy in the UK and Europe: A Phenotype-Based Analysis of Survival and System-Level Implications

BACKGROUND: Whether peritoneal dialysis (PD) is associated with lower mortality than hemodialysis (HD) in contemporary practice remains debated, particularly across heterogeneous patient populations and in the presence of competing transplantation. We examined modality-associated mortality differences across data-driven phenotypes of incident dialysis patients in the United Kingdom (UK) using a competing-risks framework. METHODS: We analysed 96,809 adults initiating dialysis in the UK Renal Registry between 2007 and 2021. Unsupervised k-prototypes clustering was used to derive phenotypes based on age, sex, ethnicity, primary kidney disease, hemoglobin, serum albumin, and transplant-listing status. Mortality during the dialysis phase prior to transplantation was analysed using competing-risks methods, treating kidney transplantation as a competing event. Cumulative incidence of death at one and five years was modelled using jack-knife pseudo-value regression with complementary log-log links, adjusting for demographic and clinical covariates. Dialysis modality (HD vs PD) was the primary exposure, with stratified analyses performed within each phenotype. A complementary competing-risks analysis examined time to transplantation. RESULTS: Among incident patients, 24% initiated PD and 76% HD. Three reproducible phenotypes were identified, differing primarily by age, hemoglobin and albumin levels, and transplant-listing status. Across the overall cohort, HD was associated with a higher cumulative incidence of death prior to transplantation at both 1 year (subdistribution hazard ratio [sHR] 1.85, 95% confidence interval [CI] 1.75-1.96) and 5 years (sHR 1.47, 95% CI 1.43-1.51). In stratified analyses, HD was associated with higher mortality across all phenotypes. At one year, adjusted sHRs ranged from 1.55 (95% CI 1.44-1.68) to 2.29 (95% CI 1.87-2.80) across clusters. At five years, the association persisted but attenuated with increasing age, with adjusted sHRs of 2.42 (95% CI 2.23-2.63) in the youngest phenotype, 1.55 (95% CI 1.48-1.61) in the intermediate phenotype, and 1.14 (95% CI 1.11-1.19) in the oldest phenotype. In complementary analyses, time to transplantation did not differ significantly across phenotypes after adjustment. CONCLUSIONS: In contemporary UK practice, hemodialysis was associated with higher mortality during the dialysis phase compared with peritoneal dialysis across distinct patient phenotypes, with time-dependent variation in effect magnitude. These registry-based associations support consideration of phenotype-informed modality selection while acknowledging the potential for residual confounding and the influence of health-system context.