Influence of allocation concealment and intention-to-treat analysis on treatment effects of physical therapy interventions in low back pain randomised controlled trials: a protocol of a meta-epidemiological study

INTRODUCTION: Meta-epidemiological studies examining the influence of methodological characteristics, such as allocation concealment and intention-to-treat analysis have been performed in a large number of healthcare areas. However, there are no studies investigating these characteristics in physical therapy interventions for patients with low back pain. The aim of this study is to investigate the influence of allocation concealment and the use of intention-to-treat analysis on estimates of treatment effects of physical therapy interventions in low back pain clinical trials. METHODS AND ANALYSIS: Searches on PubMed, Embase, Cochrane Database of Systematic Reviews, Physiotherapy Evidence Database (PEDro) and CINAHL databases will be performed. We will search for systematic reviews that include a meta-analysis of randomised controlled trials that compared physical therapy interventions in patients with low back pain with placebo or no intervention, and have pain intensity or disability as the primary outcomes. Information about selection (allocation concealment) and attrition bias (intention-to-treat analysis) will be extracted from the PEDro database for each included trial. Information about bibliographic data, study characteristics, participants’ characteristics and study results will be extracted. A random-effects model will be used to provide separate estimates of treatment effects for trials with and without allocation concealment and with and without intention-to-treat analysis (eg, four estimates). A meta-regression will be performed to measure the association between methodological features and treatment effects from each trial. The dependent variable will be the treatment effect (the mean between-group differences) for the primary outcomes (pain or disability), while the independent variables will be the methodological features of interest (allocation concealment and intention-to-treat analysis). Other covariates will include sample size and sequence generation. ETHICS AND DISSEMINATION: No ethical approval will be required for this study. The study findings will be published in a peer-reviewed journal and presented at international conferences. REGISTRATION NUMBER: International Prospective Register of Systematic Reviews (CRD42016052347).