title: N-of-1 trials are a tapestry of heterogeneity.
abstract: To summarize the methods of design, analysis, and meta-analysis used in N-of-1 trials.
  
  
  
  Electronic search for English language articles published from 1950 to 2013. N-of-1 trials were selected if they followed an ABAB design and if they assessed a health intervention for a medical condition. Elements of design, analysis, and meta-analysis were extracted.
  
  
  
  We included 100 reports representing 1,995 participants. N-of-1 trials have been conducted in over 50 health conditions. Most reports incorporated the use of elements that maintain methodological rigor, including randomization, blinding, and formal outcome assessment; however, many failed to address trial registration, funding source, and adverse events. Most reports statistically analyzed individual N-of-1 trials; however, only a small proportion of included series meta-analyzed their results.
  
  
  
  N-of-1 trials have the ability to assess treatment response in individual participants and can be used for a variety of health interventions for a wide range of medical conditions in both clinical and research settings. Considerable heterogeneity exists in the methods used in N-of-1 trials.
authors.affiliation: Department of Pediatrics, University of Alberta, 1702 College Plaza, 8215-112 Street NW, Edmonton, Alberta T6G 2C8, Canada.
authors.forename: Salima
authors.initials: S
authors.lastname: Punja
authors.affiliation: Department of Pediatrics, University of Alberta, 1702 College Plaza, 8215-112 Street NW, Edmonton, Alberta T6G 2C8, Canada; Knowledge Utilization Studies Program, Faculty of Nursing, University of Alberta, 3rd Floor Edmonton Clinic Health Academy, Edmonton, Alberta T6G 1C9, Canada.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Bukutu
authors.affiliation: Clinical Epidemiology Program, Ottawa Hospital Research Institute, Center for Practice Changing Research Building, 501 Smyth Road, PO Box 201B, Ottawa, Ontario K1H 8L6, Canada.
authors.forename: Larissa
authors.initials: L
authors.lastname: Shamseer
authors.affiliation: Department of Library Services, Children's Hospital of Eastern Ontario, 401 Smyth Road, Ottawa, Ontario K1H 8L1, Canada.
authors.forename: Margaret
authors.initials: M
authors.lastname: Sampson
authors.affiliation: Alberta Research Centre for Health Evidence, Department of Pediatrics, University of Alberta, 4-472 Edmonton Clinic Health Academy, 11405-87 Avenue, Edmonton, Alberta T6G 1C9, Canada.
authors.forename: Lisa
authors.initials: L
authors.lastname: Hartling
authors.affiliation: Information & Evaluation Services for Addiction & Mental Health, Addiction and Mental Health, Alberta Health Services-Edmonton Zone, 9942 108 Street, Edmonton, Alberta T5K 2J5, Canada.
authors.forename: Liana
authors.initials: L
authors.lastname: Urichuk
authors.affiliation: Complementary and Alternative Research and Education Program (CARE), Department of Pediatrics, University of Alberta. Electronic address: svohra@ualberta.ca.
authors.forename: Sunita
authors.initials: S
authors.lastname: Vohra
mesh_terms: D035843:Biomedical Research / Q000592:standards*; D002986:Clinical Trials as Topic / Q000592:standards*; D017408:Guidelines as Topic; D006801:Humans; D011643:Publishing / Q000592:standards*; D012107:Research Design / Q000592:standards*; D058028:Research Report / Q000592:standards*; D009626:Terminology as Topic
keywords: Analysis; Clinical trial; Evidence-based medicine; Meta-analysis; N-of-1 trial; Systematic review