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Statistical analysis plan for the Stroke Oxygen Study (SO2S): a multi-center randomized controlled trial to assess whether routine oxygen supplementation in the first 72 hours after a stroke improves long-term outcome

Julius Sim1*, Richard Gray2, Tracy Nevatte3, Andrew Howman4, Natalie Ives4 and Christine Roffe15

Author Affiliations

1 Health Services Research Unit, Keele University, Keele ST5 5BG, UK

2 Clinical Trial Service Unit, University of Oxford, Roosevelt Drive, Oxford OX3 7LF, UK

3 Stroke Research, Institute for Science and Technology in Medicine, Keele University, Keele ST5 5BG, UK

4 Birmingham Clinical Trials Unit, Robert Aitken Institute, University of Birmingham, Birmingham B15 2TT, UK

5 Stroke Research, North Staffordshire Combined Healthcare NHS Trust, Holly Lodge, 62 Queens Road, Stoke on Trent, Staffordshire ST4 7LH, UK

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Trials 2014, 15:229  doi:10.1186/1745-6215-15-229

Published: 16 June 2014



The Stroke Oxygen Study (SO2S) is a multi-center randomized controlled trial of oxygen supplementation in patients with acute stroke. The main hypothesis for the trial is that fixed-dose oxygen treatment during the first 3 days after an acute stroke improves outcome. The secondary hypothesis is that restricting oxygen supplementation to night time only is more effective than continuous supplementation. This paper describes the statistical analysis plan for the study.

Methods and design

Patients (n = 8000) are randomized to three groups: (1) continuous oxygen supplementation for 72 hours; (2) nocturnal oxygen supplementation for three nights; and (3) no routine oxygen supplementation. Outcomes are recorded at 7 days, 90 days, 6 months, and 12 months. The primary outcome measure is the modified Rankin scale at 90 days. Data will be analyzed according to the intention-to-treat principle. Methods of statistical analysis are described, including the handling of missing data, the covariates used in adjusted analyses, planned subgroups analyses, and planned sensitivity analyses.

Trial registration

This trial is registered with the ISRCTN register, number ISRCTN52416964 (30 September 2005).

hypoxia; oxygen supplementation; randomized controlled trial; statistical analysis plan; stroke