Assessing the quality of evidence for preterm labor tocolytic trials

OBJECTIVE: To assess the quality of tocolysis randomized controlled trials (RCTs) and to determine trial factors contributing to better quality evidence.

METHODS: The Cochrane Central Register of Controlled Trials, MEDLINE, MEDLINE In-Process, EMBASE and CINAHL were searched for terms "preterm labor," "tocolytic" or "obstetric labor, premature" up to 1 August 2009.Data regarding study design, characteristics, number of participants and outcomes reported were extracted by at least two review authors. Study quality was assigned using the Cochrane Collaboration Handbook methodology and categories. Trends for quality over time, the impact of study size and the individual drugs compared were analyzed for impact on overall quality of trials.

RESULTS: Of the 3197 titles initially identified, 89 RCTs of tocolytic therapy were reviewed. Of the six quality areas, 10 (11.2%) trials satisfied all areas, while only one trial (1.1%) met one area. The mean number of adequate areas was 4.1 ± 1.2. Overall, 52 (58.4%) of the trials achieved high-quality categorization. Controlling for multiple trial factors, the trial continent and decade were significant predictors of overall trial quality.

CONCLUSION: The majority of tocolysis RCTs are of high quality. Larger trials, more recent trials and placebo-controlled trials were associated with higher quality scores.