This observational study will compare cardiovascular status, bone mineral metabolism, systemic inflammation, body composition, functional status, quality of life, pruritus, and pain among patients receiving different renal replacement therapy modalities and healthy controls.

Adult participants will be included in four groups: maintenance hemodialysis, continuous ambulatory peritoneal dialysis, automated peritoneal dialysis, and healthy controls. No new treatment, drug, dialysis modality, or experimental device will be assigned as part of the study. Participants will continue their routine clinical care.

Serum interleukin-6 (IL-6), vascular cell adhesion molecule-1 (VCAM-1), fibroblast growth factor-23 (FGF-23), and sclerostin levels will be measured. Arterial stiffness will be assessed using pulse wave velocity (PWV), and body composition will be assessed using the Body Composition Monitor (BCM). Handgrip strength, quality of life, pruritus, and pain scores will also be evaluated.

The study will also explore correlations between biochemical biomarkers, arterial stiffness, body composition, and patient-reported outcomes. In the automated peritoneal dialysis group, objective treatment adherence will additionally be assessed using the Sharesource (Baxter/Vantive) cloud-based remote patient monitoring platform.

Patients with end-stage kidney disease receiving renal replacement therapy have a high burden of cardiovascular disease, chronic inflammation, mineral and bone metabolism abnormalities, altered body composition, impaired quality of life, pruritus, and pain. Hemodialysis and peritoneal dialysis differ in clearance patterns, fluid management, and treatment delivery, which may influence biochemical, vascular, nutritional, and patient-reported outcomes.

This is a single-center observational clinical study including adult patients receiving routine renal replacement therapy and healthy controls. Participants will not be assigned to any intervention by the study protocol. Hemodialysis, continuous ambulatory peritoneal dialysis (CAPD), and automated peritoneal dialysis (APD) treatments will continue according to routine clinical practice and the decisions of the treating physicians.

The study will include 100 participants in four groups: 40 patients receiving maintenance hemodialysis, 20 patients receiving CAPD, 20 patients receiving APD, and 20 healthy controls. Dialysis patients will be evaluated at baseline, Month 3, Month 6, and Month 12. Healthy controls will be evaluated at baseline only.

The main objective is to compare patients receiving different dialysis modalities and healthy controls in terms of bone mineral metabolism, systemic inflammation, endothelial dysfunction, arterial stiffness, body composition, functional status, quality of life, pruritus, and pain. Serum sclerostin and fibroblast growth factor-23 (FGF-23) will be evaluated as bone mineral metabolism biomarkers. Serum interleukin-6 (IL-6) and vascular cell adhesion molecule-1 (VCAM-1) will be evaluated as inflammatory and endothelial dysfunction-related biomarkers. These biomarkers will be measured using enzyme-linked immunosorbent assay (ELISA).

For hemodialysis patients, blood samples will be obtained immediately before a mid-week dialysis session through the existing vascular access. For CAPD patients, APD patients, and healthy controls, fasting venous blood samples will be obtained in the morning. Serum samples will be processed and stored according to laboratory procedures until batch analysis.

Arterial stiffness will be assessed using pulse wave velocity (PWV). Body composition and fluid status will be assessed by bioimpedance analysis using the Fresenius Body Composition Monitor (BCM). Body composition parameters will include overhydration, extracellular water to total body water ratio, intracellular water, lean tissue index, body cell mass. Handgrip strength will be measured as a functional parameter.

Patient-reported outcomes will be assessed using the Kidney Disease Quality of Life-36 (KDQOL-36), the Uremic Pruritus in Dialysis Patients (UP-Dial) questionnaire, and the Short-Form McGill Pain Questionnaire (SF-MPQ), as applicable. In healthy controls, kidney disease-specific questionnaire components will not be applied; instead, the 12-Item Short Form Health Survey (SF-12) will be used to assess general health-related quality of life.

The study will also evaluate correlations between molecular biomarkers, instrumental measurements, and clinical scores. Specifically, the relationships between elevated biomarker levels, increased arterial stiffness, altered body composition, lower quality of life, pruritus, and pain burden will be explored.

As an additional objective, objective treatment adherence will be assessed in the APD group using data transferred from home cycler devices to the Sharesource (Baxter/Vantive) cloud-based remote patient monitoring platform. Adherence-related variables will include the percentage of completed sessions, lost dwell time, differences between prescribed and delivered ultrafiltration, and device bypass or manual intervention alarms. Full treatment adherence will be defined as completion of at least 90% of the prescribed dialysis session number and total prescribed dialysis duration.

No additional invasive procedure will be performed other than standard blood sampling for biomarker measurements. Pulse wave velocity and body composition measurements are non-invasive and will be performed using devices used in routine clinical practice.

Inclusion Criteria:

• Age 18 to 80 years.
• For dialysis cohorts: diagnosis of end-stage kidney disease and receiving maintenance hemodialysis or peritoneal dialysis.
• For dialysis cohorts: receiving regular hemodialysis, continuous ambulatory peritoneal dialysis, or automated peritoneal dialysis for at least 6 months.
• For healthy controls: no known kidney disease, with estimated glomerular filtration rate greater than 90 mL/min/1.73 m².
• For healthy controls: no known systemic inflammatory disease or active malignancy.
• Able to comply with planned study procedures, including pulse wave velocity measurement, Body Composition Monitor assessment, questionnaires, and biomarker measurements.
• Able and willing to provide written informed consent.

Exclusion Criteria:

• Inability to comply with study measurements or questionnaire assessments.
• Refusal or inability to provide written informed consent.
• Age younger than 18 years or older than 80 years.
• Acute infection.
• Recent major surgical intervention.
• Active malignancy.
• Terminal illness with limited life expectancy.
• Mental, cognitive, physical, or clinical condition preventing participation in study procedures.

Adult participants will be recruited from the Gazi University Faculty of Medicine nephrology outpatient clinic and dialysis units. The study population will include four cohorts: patients receiving maintenance hemodialysis, patients receiving continuous ambulatory peritoneal dialysis, patients receiving automated peritoneal dialysis, and healthy controls without known kidney disease. Dialysis patients must have been receiving regular dialysis treatment for at least 6 months. Healthy controls will have no known kidney disease, systemic inflammatory disease, or active malignancy.

Individual participant data (IPD) are not planned to be shared publicly. The study is a single-center observational study with a limited number of participants, and the dataset may include sensitive clinical, laboratory, questionnaire, and treatment adherence data. All data will be stored in coded form and managed in accordance with institutional policies, ethical requirements, and applicable data protection regulations. De-identified aggregate results may be reported in scientific publications.