First-year physical function trajectories and adverse outcomes in incident peritoneal dialysis: a prospective cohort protocol

Peritoneal dialysis (PD) is a key renal replacement therapy for end-stage kidney disease, yet early trajectories of physical function following PD initiation are heterogeneous and clinically consequential. The Peritoneal Dialysis-Physical Function (PD-PF) cohort study protocol aims to: (1) identify distinct 12‑month physical function trajectories after PD initiation; (2) develop prediction models using baseline and early follow-up data to classify patients into trajectory groups; and (3) examine associations of baseline physical function and trajectory membership with adverse clinical outcomes. We will enroll incident adult PD patients within 30 days after catheter placement. Assessments are scheduled at baseline (month 0) and at months 3, 6, 9, and 12, allowing a ± 4‑week window. Physical function is assessed by cardiopulmonary exercise testing, handgrip strength, five-times sit-to-stand, and 4-meter usual gait speed. Primary objective is to identify heterogeneous physical function trajectories over 12 months using multivariate group-based trajectory modeling jointly on the four physical function measures. We will then develop penalised multinomial logistic prediction models to classify trajectory membership using baseline predictors. Associations between baseline physical function and trajectory groups with adverse outcomes will be estimated using Cox proportional hazards models with prespecified covariate adjustment and Fine-Gray competing risks analyses will be performed for selected non-fatal outcomes as sensitivity analyses. The PD-PF study was approved by the institutional ethics committee (approval No. 2025LCSY082), and the study will be conducted in accordance with the principles of the Declaration of Helsinki and the Strengthening the Reporting of Observational Studies in Epidemiology guidelines. Written informed consent will be obtained from all participants. Results will be disseminated via peer‑reviewed publications and conference presentations, with deidentified data summaries shared upon reasonable request in accordance with institutional and regulatory policies. The study aims to inform risk stratification and targeted, function‑focused interventions in incident PD populations. Registered Report Identifier: ChiCTR2500108025. Date of registration; 2025-08-22.