Study procedures shown in italic are routine clinical practice procedures. Information from these procedures is expected to be available as part of routine clinical practice. If not routinely collected, it should be recorded in the electronic study case record form as non-available data.

*Participants are followed for at least 24 months. That means that for the first patient, the follow-up time will be the enrolment time up to the last patient in (12 months) plus the follow-up time of the last patient in (24 months). So there will be patients that have visits scheduled at 27 months, 30 months, 33 months and 36 months.

†Subjects randomised to high-dose HDF can continue the study after higher convection volume of ≥23 L in postdilution mode is reached. The reason for not reaching higher convection volume should be recorded.

‡Systolic and diastolic blood pressure and heart rate should be measured once before and after dialysis in a sitting position. The body weight before and after dialysis will be measured and reported.

§In case of vascular access (native fistula or graft) the results of vascular access flow assessment should be recorded at least twice a year (if available).

¶The following laboratory values will be recorded (incl. units) before dialysis (if available): haemoglobin, sodium, potassium, calcium, phosphate, creatinine, urea, magnesium, parathyroid hormone, C-reactive protein and residual renal function (urine sampling). After dialysis the following laboratory values will be recorded (incl. units): urea and creatinine. Single-pool Kt/V urea will be calculated and recorded together with the calculation method.

**The following concomitant medication, including dosage and frequency, will be recorded during screening: Antihypertensives: agents affecting the renin-angiotensin system, beta blockers; lipid modifying medication; medication used for diabetes; heparin; erythropoiesis stimulating agents; Iron preparations; drugs for treatment of hyperkalaemia; phosphate binders; vitamin D and vitamin D analogues; PTH antagonists. The following concomitant medication, including dosage and frequency, will be recorded during all study visits: Drugs for treatment of hyperkalaemia; phosphate binders; vitamin D and vitamin D analogues; PTH antagonists; erythropoiesis stimulating agents; medication used to treat SAEs.

††During the Screening visit the Patient Health Assessment Screening should be completed. During all other study visits the Patient Health Assessment quarterly. In between the study visits, during the first 12 months of study conduct the Patient Health Assessment Monthly should be completed every month. Questionnaires need to be completed within the first hour after the dialyses has started.

‡‡The following dialysis specifics will be recorded for all subjects: type of dialyser, delivered blood flow rate in the extracorporeal circuit, dialysis session time, anticoagulation, type vascular access, net ultrafiltration volume (=desired weight loss). Additional dialysis specifics will be recorded for subjects receiving high-dose HDF: achieved convection volume, substitution volume and number of treatment sessions not performed as HDF in the previous 3 months.

§§SAEs will be assessed from the signing of the Informed Consent Form until end of the study for the subject. If the subject drops out (eg, due to kidney transplantation) he/she will be followed for mortality and morbidity until the end of the study.

EOT, end of treatment; HDF, haemodiafiltration; PTH, parathyroid hormone; SAE, serious adverse event.