Fig. 1

Flow diagram. AEs = adverse events; DARE = Cochrane Database of Abstracts of Reviews of Effects; HTA = Cochrane Health Technology Assessment Database; RCT = randomized controlled trial; SMT = spinal manipulative therapy; SRs = systematic reviews. *Non-systematic: does not report to have searched at least two electronic databases or does not document an assessment of the quality of the included studies (case reports, case series, cross-sectional studies and surveys were not required to have been quality assessed). † The DARE database stopped updating March 2015. ‡ Four of these protocols resulted in a systematic review which was retrieved in the updated search