Here is the design of a clinical trial:

Official Title: A Randomised Pragmatic Trial Of Corticosteroid Optimisation In Severe Asthma Using A Composite Biomarker Algorithm To Adjust Corticosteroid Dose Versus Standard Care

Included conditions:
- Severe Persistent Asthma

Study Armgroups:
- {'label': 'Biomarker arm', 'type': 'EXPERIMENTAL', 'description': 'Biomarker based adjustment of corticosteroid dose.', 'interventionNames': ['Other: Biomarker based adjustment of corticosteroid dose']}
- {'label': 'Standard care', 'type': 'NO_INTERVENTION', 'description': "The subject's corticosteroid dose will be adjusted based upon asthma symptom control and lung function"}

Interventions:
- {'type': 'OTHER', 'name': 'Biomarker based adjustment of corticosteroid dose', 'description': "The subject's corticosteroid dose will be adjusted based upon biomarker results (FeNO, eosinophils and periostin)", 'armGroupLabels': ['Biomarker arm']}

Primary Outcomes:
- {'measure': 'Proportion of patients with any reduction in corticosteroid dose', 'description': 'Proportion of patients with any reduction in oral or inhaled corticosteroid dose at any point over the 48 weeks of the study', 'timeFrame': '48 weeks'}

Please estimate the sample size based on the assumption: 
The study assumes a 20% dropout rate, >80% power, and a two-sided significance level of α = 0.05, using the continuity-corrected chi-squared test for proportions.
Power and sample size estimate
        The primary efficacy endpoint of this study is the proportion of patients who achieve any reduction in ICS or OCS dose from baseline to week 48. It is estimated that up to 10% of the patients in the symptom-based algorithm (control) group will achieve a reduction in ICS or OCS. Operating characteristics for achieving additional reductions in the biomarker-based algorithm (active intervention) group are provided in TableÂ 6, with 200, 300, and 400 subjects with each scenario assuming a patient drop-out rate of 20% by week 48 withâ>â80% power at the two-sided Î±â=â0.05 significance level with use of the continuity-corrected chi-squared test for proportions.Table 6Operating characteristics for detecting differences in the primary endpointTotal N(interventionâ+âcontrol)RatioType 1 errorProportion of patients achieving a reduction in ICS or OCSPowerControlInterventionDifference400 (320â+â80)4:10.0510%26%16%83%300 (240â+â60)4:10.0510%29%19%83%200 (160â+â40)4:10.0510%34%24%83%Assumes a 20% drop out rateICS inhaled corticosteroid, OCS oral corticosteroid
        Efficacy analyses will be conducted on an intent-to-treat (ITT) population consisting of all randomised participants who completed at least one post-baseline efficacy assessment, with patients allocated to the group to which they were randomised. The number and proportion of patients who enrol, discontinue, and complete the study will be tabulated by the Trial Management Group. Reasons for early termination from the study will be listed and summarised by Trial Management Group. Any eligibility criteria exceptions and other major protocol deviations will also be summarized by the Trial Management Group. A full CONSORT diagram (Fig.Â 1) will be produced for the study including patients screened and reason for screen failure. Demographic and baseline characteristics (e.g. age, sex, ethnicity, weight, FEV1) will be summarized for all randomised patients by the Trial Management Group using descriptive statistics.Fig. 1CONSORT diagram displaying flow of patients through the RASP-UK biomarker study