Threats to reliability risk erroneous conclusions: a survey of prospective registration and sample sizes of randomised trials in women's health.

OBJECTIVE: Prospective registration of clinical trials has been required since 2005. We aimed to assess concordance between registered and reported sample sizes among prospectively registered randomised controlled trials (RCTs) in obstetrics and gynaecology. DESIGN: Analysis of prospectively registered and published data. SETTING: Women's health. SAMPLE: Obstetrics and gynaecology RCTs published in eight journals in 2015. METHODS: Specialist (Acta Obstet Gynecol Scand, BJOG, Obstet Gynecol and Am J Obstet Gynecol) and general (BMJ, N Engl J Med, JAMA and Lancet) journals were searched from 1 January to 31 December 2015 for main reports of obstetrics and gynaecology RCTs. Their corresponding registries and protocols were sought and data were extracted. Proportions and 95% CI were calculated using exact methods. MAIN OUTCOME MEASURES: Prospective registration of RCT and sample size concordance between RCTs and their registries within those where registration took place before patients were recruited. RESULTS: Of the 75 relevant RCTs, 51 (68%, 95% CI 56-78%, P < 0.001 using a null hypothesis requiring 100% compliance) were prospectively registered, a feature found to be more common in general journals versus specialist journals (21/22 versus 30/53, 95% versus 57%, P = 0.001). Of the 51 prospectively registered RCTs, 31 (61%, 95% CI 46-74%, P = 0.003 using a null hypothesis requiring 40% of studies to achieve their stated sample size) did not reach the target sample size. CONCLUSIONS: There are gaps in universal adoption of the prospective trial registration rule. Inability to meet target sample size risks deficiencies in statistical power with unreliability in results. TWEETABLE ABSTRACT: Only two-thirds of RCTs in women's health are prospectively registered, and over half fail to achieve target sample sizes.

Participation in clinical trials improves outcomes in women's health: a systematic review and meta-analysis.

BACKGROUND: Previous reviews examining the effect of participation in trials on outcomes have not consistently shown benefit. Obstetrics and gynaecology is a unique disease area posing challenges for both researchers and patients. OBJECTIVES: To determine whether participation in randomised controlled trials (RCTs), compared with non-participation, has a beneficial effect on women's health. SEARCH STRATEGY: Medline, Embase, the Cochrane Library, and PsycInfo were searched up to December 2015. SELECTION CRITERIA: We selected studies that reported the same clinical outcomes for participants in a women's health RCT and a comparable non-participant cohort. DATA COLLECTION AND ANALYSIS: Data were extracted on quality, characteristics and study results. Outcomes were compared using logistic regression. MAIN RESULTS: There were 21 relevant studies (20 160 women, 4759 outcome events). Trial participants, compared with non-participants, had 25% better odds of improved outcomes on average (OR 0.75; 95% CI 0.64-0.87; I2  = 64.3%). The beneficial effect of participating in a trial was larger in comparisons where: RCTs were of high quality (OR 0.62; 95% CI 0.50-0.76) versus low (OR 0.92; 95% CI 0.74-1.16); and RCT intervention was not available to non-participants (OR 0.57; 95% CI 0.47-0.69) versus when it was (OR 1.13; 95% CI 0.89-1.44). The effect of trial participation was not influenced by effect size within the RCT (P = 0.48), whether funding was received or not (P = 0.13), whether non-participants received any treatment or not (P = 0.49), and the quality of the comparison of RCT participants with non-participants (P = 0.88). CONCLUSIONS: Women participating in RCTs on average experienced better outcomes compared with those outside trials. TWEETABLE ABSTRACT: Participants in obstetric and gynaecology RCTs experience better outcomes compared with non-participants.