How often is the core outcome set for low back pain used in clinical trials? A protocol for a meta-epidemiological study

BackgroundNon-specific Low back pain (NSLBP) is the worldwide leading cause of disability, accounting for large costs for healthcare systems and work productivity. Many treatment options are available for patients with NSLBP. Authors of systematic reviews on LBP report that outcomes are often measured and reported inconsistently. This inconsistency limits the comparison of findings among trials, and it can be due to selective outcome reporting bias (e.g. reporting only outcomes with positive results in a publication), which strongly affects the conclusions of systematic reviews. Recommendations for standardised reporting of outcome measurement instruments in clinical studies were initially publicated in 1998 and updated through an international consensus Delphi study by Chiarotto and colleagues in 2015. This updated Core Outcome Set (COS) for NSLBP included the following core outcome domains: "physical functioning", "pain intensity", "health-related quality of life", and "number of deaths". With the exception of "number of deaths", the other three core domains were already included in the core set publicated in 1998 by Deyo et al. In 2018, another international consensus of Chiarotto et al. formulated recommendations on which core outcome measurement instruments (Core Outcome Measurement Set - COMS) should be used in NSLBP trials. A consensus was reached on Numeric Rating Scale (NRS) for "pain intensity", Oswestry Disability Index (ODI) or Roland-Morris Disability Questionnaire (RMDQ-24) for "physical functioning", Short Form Health Survey 12 (SF12) or 10-item PROMIS Global Health (PROMIS-GH-10) for "HRQOL". Therefore, the recommended COS has been in the public domain for more than 20 years. However, it is still unknown whether it has changed the selection of outcomes used in NSLBP trials during this period. Objectives(1)To assess the uptake of the COS for NSLBP in clinical trials; (2)To assess the uptake of the Core Outcome Measurement Set for NSLBP in clinical trials; (3)To analyse whether specific study characteristics (year of registration, sample size, country of origin, duration of follow-up, phase of the trial, intervention, and source of funding) are associated with the COS uptake MethodsWe will adopt Kirkham et al.s recommendations on the assessment of COS uptake. We will search the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) and Clinicaltrials.gov registry to identify potentially eligible trial protocols. Two reviewers (TI and SG) will select potentially eligible entries and evaluate whether they meet the eligibility criteria. A consensus meeting will be held to determine agreement on the selection; in case of disagreement, a third reviewer (SS) will decide on inclusion. We will calculate the percentage of clinical trials that planned to measure data on the NSLBP full COS. We will also calculate the proportion of trials that reported the percentage of trials measuring the full COS per year. We will calculate the percentage of the NSLBP core outcome measurement instruments used per each domain described in the COS. Lastly, we will perform a multivariable logistic regression analysis to assess the relationship between the full COS uptake (yes/no) as the dependent variable and the following independent variables: year of registration, sample size, country of origin, duration of follow-up interval, phase of the trial (III or IV), intervention (pharmacological trial vs non-pharmacological trial), and source of funding (commercial vs non-commercial vs no funding). Ethics and disseminationA manuscript will be prepared and submitted for publication in an appropriate peer-reviewed journal upon study completion. We believe that the results of this investigation will be relevant to researchers paying more attention to the synthesis of the evidence to translate clinical implications to key stakeholders (healthcare providers and patients).