To assess whether reported trial quality or trial characteristics are associated with trial outcome.
Study Design and Setting
We identified all eligible randomized controlled trials (RCTs) of arthroplasty from 1997 and 2006. Trials were classified based on whether the main trial outcome was reported to be positive (n=90) or negative (n=94). Multivariable logistic regression analyses studied the association of reporting of trial quality measures (blinding, placebo use, allocation procedure; overall quality) and trial characteristics (intervention type, number of patients/centers, funding) with positive trial outcome.
RCTs that used placebo or blinded care providers, used pharmacological interventions, had higher Jadad quality scores or sample size >100 patients were significantly more likely to report positive result in univariate analyses. Multivariable regression did not identify methodological quality of RCTs, but rather that sample size, was associated with trial outcome. Studies with >100 patients were 2.2 times more likely to report a positive result than smaller studies (p=0.04).
Lack of association of reported trial quality with positive outcome in multivariable analyses suggests that previously observed association of reported study quality with study outcome in univariate analyses may be mediated by other study characteristics, such as study sample size.
- Arthroplasty RCTs with sample size of 100 patients or more are significantly more likely to report a positive rather than a negative outcome.
- RCT quality was not associated with study outcome (positive vs. negative) in multivariable analyses, in contrast to previous studies that found an association of quality with outcomes in univariate analyses that did not adjust for sample size or type of intervention.
- Previously reported associations of study quality and outcomes may have been mediated by these characteristics.
- Future studies examining correlates of study outcomes should control for sample size, study quality and type of intervention.
Keywords: Assessment, Quality, Arthroplasty, Randomized Controlled Trial, Trial Outcome