“The design to affirm causality is the randomized controlled trial (RCT) using placebo and double-blind. So how to evaluate the effectiveness of osteopathy if manual placebo is not possible? What are the most appropriate study designs for this type of practice? The differences observed between the results of experimental studies (RCTs) and other types of studies addressing the same theme in the context of evaluating the effectiveness of non-drug interventions (NDIs) on intestinal functional disorders (IFDs) concern, in addition to study designs, the size of the effect and the risk of bias. No comparison of effect size estimates from all experimental or non-experimental study designs used to evaluate the effectiveness of NDIs on IFDs was undertaken. We therefore propose to conduct a systematic review whose objective is first to compare the results of RCTs with the results of observational and quasi-experimental studies and then to assess whether differences in risk of bias justify differences in observed effect sizes based on a bias risk analysis (Anglemyer et al., 2014).
We will estimate a ratio of odds ratios (ROR) in each meta-analysis using RCTs as the reference group. In order to obtain an average ROR comparing the results of RCTs with the results of quasi-experimental and observational studies, we will combine the RORs obtained for each meta-analysis by performing a random effects meta-analysis (Sterne et al., 2002). Sub-group analysis will be conducted according to the type of NDI (Shamseer et al., 2015).
The review’s conclusions will make it possible to propose a new study design to overcome these methodological shortcomings.”