Here is the design of a clinical trial:

Official Title: Does Incremental Initiation of Haemodialysis Preserve Native Kidney Function? A Multicentre Feasibility Randomised Controlled Trial

Included conditions:
- Kidney Failure
- Dialysis

Study Armgroups:
- {'label': 'Standard Haemodialysis', 'type': 'OTHER', 'description': 'Thrice weekly dialysis (control arm) - dialysis dose will not be adjusted according to Residual Kidney Function and subjects will be dialysed initially for 3.5-4 hours thrice weekly to ensure a target minimum eKt/V of 1.2.', 'interventionNames': ['Procedure: Standard Haemodialysis']}
- {'label': 'Incremental dialysis', 'type': 'EXPERIMENTAL', 'description': 'Twice weekly dialysis - dialysis dose will be adjusted according to Residual Kidney Function.\n\nPatients will commence dialysis for 3.5-4 hours twice weekly and have residual renal urea clearance formally measured by interdialytic urine collection at the end of the week following dialysis initiation. Subsequent to this, dialysis dose will be adjusted.', 'interventionNames': ['Procedure: Incremental dialysis']}

Interventions:
- {'type': 'PROCEDURE', 'name': 'Standard Haemodialysis', 'description': 'Thrice weekly dialysis.', 'armGroupLabels': ['Standard Haemodialysis']}
- {'type': 'PROCEDURE', 'name': 'Incremental dialysis', 'description': 'Individualised dialysis dose according to native kidney function.', 'armGroupLabels': ['Incremental dialysis']}

Primary Outcomes:
- {'measure': 'Recruitability', 'description': 'Number of patients potentially eligible for screening during the study period', 'timeFrame': '12 months'}
- {'measure': 'Recruitability', 'description': 'Proportion of screened patients who fulfil study criteria.', 'timeFrame': '12 months'}
- {'measure': 'Recruitability', 'description': 'Proportion of patients approached who agree to participate in the study.', 'timeFrame': '12 months'}
- {'measure': 'Retainability', 'description': 'Proportion of patients randomised who withdraw from the study and the reasons for their withdrawal.', 'timeFrame': '12 months'}
- {'measure': 'Protocol Adherence', 'description': 'Proportion of patients who adhere to protocol dialysis frequency.', 'timeFrame': '12 months'}
- {'measure': 'Incidence of hospital admissions due to hyperkalemia, fluid overload, lower respiratory tract infection [Safety of the study]', 'description': 'Frequency of hospital admission due to hyperkalemia and fluid overload, and lower respiratory tract infection (LRTI).', 'timeFrame': '12 months'}
- {'measure': 'Effect size', 'description': 'Rate of change (mean) of RKF in the first 6 months after randomisation.', 'timeFrame': '6 months after randomisation'}
- {'measure': 'Dialysis dose', 'description': 'Dialysis dose measured by eKT/V', 'timeFrame': '6 months after randomisation'}
- {'measure': 'Residual kidney function', 'description': 'Residual kidney function measured by eKT/V', 'timeFrame': '6 months after randomisation'}

Please estimate the sample size based on the assumption: 
Significance level and power are not explicitly mentioned. Assumes a retention rate of 75% over 6 months and a 40% eligibility rate among the incident HD population.
Sample size
        Retrospective studies suggest that decline of RKF may be attenuated in patients who receive twice weekly dialysis compared with thrice weekly, and that this effect occurs early such that a difference in RKF at 6 months is likely to be an optimal time point for the basis of a power analysis. Our initial power analysis, based on our own retrospective data,28 indicated an effect size (Cohenâs d) of 0.37 calculated from mean and SD of urea clearance slopes in the first 6 months after HD initiation between two groups of patients, one initiating HD twice weekly and the other thrice weekly. Based on this, the sample size for the proposed definitive RCT would be 180 (90 each arm). If the definitive study were to be carried out using the same four centres, the available incident HD population would be around 600 annually or 1200 over a proposed 2-year recruitment period. We anticipate that 40% of these patients will meet the eligibility criteria, that is, 480 patients. To achieve 180 analysable patients at 6 months following randomisation, we will need to recruit 50% of eligible patients assuming a retention rate of 75% over 6 months.
        This feasibility study will test these assumptions on effect size, the proportion of incident patients who can be prescreened who are eligible to be approached for study consent, the proportion of patients approached for screening who consent, pass formal screening and undergo randomisation (recruitability), and the retention rate during the 6 months after randomisation (retainability). Sample sizes between 24 and 50 have been recommended for feasibility studies.29 30 Initially, we chose a sample size of 50 but, because of a higher than anticipated recovery of renal function in the first few weeks of recruitment, increased this to 54. A sample of this size will enable us to estimate eligibility, recruitability, screen-failure rate and retainabililty rate to within a 95% CI 11% to 14%.