title: 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.
abstract: BACKGROUND
  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
  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.
  
  
  BACKGROUND
  This trial is registered with the ISRCTN register, number ISRCTN52416964 (30 September 2005).
authors.affiliation: Health Services Research Unit, Keele University, Keele ST5 5BG, UK. j.sim@keele.ac.uk.
authors.forename: Julius
authors.initials: J
authors.lastname: Sim
authors.forename: Richard
authors.initials: R
authors.lastname: Gray
authors.forename: Tracy
authors.initials: T
authors.lastname: Nevatte
authors.forename: Andrew
authors.initials: A
authors.lastname: Howman
authors.forename: Natalie
authors.initials: N
authors.lastname: Ives
authors.forename: Christine
authors.initials: C
authors.lastname: Roffe
mesh_terms: D003627:Data Interpretation, Statistical; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D009551:Night Care / Q000191:economics / Q000379:methods; D010043:Outcome and Process Assessment, Health Care / Q000191:economics / Q000379:methods*; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D016016:Proportional Hazards Models; D020127:Recovery of Function; D012107:Research Design; D020521:Stroke / Q000378:metabolism* / Q000401:mortality / Q000628:therapy*; D013995:Time