title: Rational and design of an individual participant data meta-analysis of spinal manipulative therapy for chronic low back pain-a protocol.
abstract: Chronic low back pain (LBP) is the leading cause of pain and disability, resulting in a major socioeconomic impact. The Cochrane Review which examined the effect of spinal manipulative therapy (SMT) for chronic LBP concluded that SMT is moderately effective, but was based on conventional meta-analysis of aggregate data. The use of individual participant data (IPD) from trials allows for a more precise estimate of the treatment effect and has the potential to identify moderators and/or mediators. The aim is (1) to assess the overall treatment effect of SMT for primary and secondary outcomes in adults with chronic LBP, (2) to determine possible moderation of baseline characteristics on treatment effect, (3) to identify characteristics of intervention (e.g., manipulation/mobilization) that influence the treatment effect, and (4) to identify mediators of treatment effects.
  
  
  
  All trials included in the Cochrane Review on SMT for chronic LBP will be included which were published after the year 2000, and the search will be updated. No restrictions will be placed on the type of comparison or size of the study. Primary outcomes are pain intensity and physical functioning. A dataset will be compiled consisting of individual trials and variables included according to a predefined coding scheme. Variables to be included are descriptive of characteristics of the study, treatment, comparison, participant characteristics, and outcomes at all follow-up periods. A one-stage approach with a mixed model technique based on the intention-to-treat principle will be used for the analysis. Subsequent analyses will focus on treatment effect moderators and mediators.
  
  
  
  We will analyze IPD for LBP trials in which SMT is one of the interventions. IPD meta-analysis has been shown to be more reliable and valid than aggregate data meta-analysis, although this difference might also be attributed to the number of studies that can be used or the amount of data that can be utilized. Therefore, this project may identify important gaps in our knowledge with respect to prognostic factors of treatment effects.
  
  
  
  PROSPERO CRD42015025714.
authors.affiliation: Department of Epidemiology and Biostatistics, EMGO+ Institute for Health and Care Research, VU University Medical Center, Amsterdam, Netherlands. a.de.zoete@vu.nl.|Department of Health Science, Institute for Health and Care Research, Faculty of Earth & Life Science, VU University, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands. a.de.zoete@vu.nl.
authors.forename: A
authors.identifier: 0000-0002-1421-3862
authors.initials: A
authors.lastname: de Zoete
authors.affiliation: Department of Health Science, Institute for Health and Care Research, Faculty of Earth & Life Science, VU University, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands.
authors.forename: M R
authors.initials: MR
authors.lastname: de Boer
authors.affiliation: Department of Health Science, Institute for Health and Care Research, Faculty of Earth & Life Science, VU University, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands.
authors.forename: M W
authors.initials: MW
authors.lastname: van Tulder
authors.affiliation: Department of Epidemiology and Biostatistics, EMGO+ Institute for Health and Care Research, VU University Medical Center, Amsterdam, Netherlands.|Department of Health Science, Institute for Health and Care Research, Faculty of Earth & Life Science, VU University, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands.
authors.forename: S M
authors.initials: SM
authors.lastname: Rubinstein
authors.affiliation: Warwick Clinical Trials Unit, Warwick Medical School, The University of Warwick, Coventry, CV4 7AL, UK.
authors.forename: M
authors.initials: M
authors.lastname: Underwood
authors.affiliation: Department of Community Health & Epidemiology, Dalhousie University, Halifax, Nova Scotia, B3H 1V7, Canada.
authors.forename: J A
authors.initials: JA
authors.lastname: Hayden
authors.affiliation: Department of Epidemiology and Biostatistics, EMGO+ Institute for Health and Care Research, VU University Medical Center, Amsterdam, Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Kalter
authors.affiliation: Department of Epidemiology and Biostatistics, EMGO+ Institute for Health and Care Research, VU University Medical Center, Amsterdam, Netherlands.|Department of Health Science, Institute for Health and Care Research, Faculty of Earth & Life Science, VU University, De Boelelaan 1085, 1081HV, Amsterdam, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Ostelo
mesh_terms: D002908:Chronic Disease; D006801:Humans; D017116:Low Back Pain / Q000628:therapy; D020393:Manipulation, Spinal / Q000379:methods; D015201:Meta-Analysis as Topic; D016896:Treatment Outcome
keywords: Individual participant data; Low back pain; Spinal manipulative therapy