1. Rady Faculty of Health Sciences, Department of Internal Medicine, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
2. Rady Faculty of Health Sciences, Department of Community Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg, Canada
3. Department of Biostatistics, University of Alabama at Birmingham, Birmingham, Alabama, USA
4. Mellen Center for Multiple Sclerosis, Neurological Institute, Cleveland Clinic, Cleveland, Ohio, USA
5. Department of Neurology, Section on Statistical Planning and Analysis, UT Southwestern Medical Center, Dallas, Texas, USA