Cross-over trials – are we doing it right? Are they doing it right?

Tags: Oral
Nolan S1, Dwan K2
1University of Liverpool, United Kingdom, 2Cochrane Cystic Fibrosis and Genetic Disorders Group, United Kingdom

Background: Previous work by Elbourne (2002) indicated that the description in the methods section of systematic reviews regarding how cross-over trial data were to be included was insufficient and recommendations were made for improvement. Recent work found that reports of cross-over trials often omit important methodological information relating to design, analysis and presentation of results.

Objectives:

- To assess review methodology for including cross-over trials in reviews published by the Cochrane Cystic Fibrosis and Genetic Disorder (CFGD) Group and to investigate whether there has been an improvement since the Elbourne results published in 2002.

- To assess the quality of reporting of cross-over trials within the trial reports themselves, and subsequently, within Cochrane Reviews.

- To establish recommendations for how cross-over data should be included in Cochrane Reviews, in line with the Methodological Expectations of Cochrane Intervention Reviews (MECIR) standards.

Methods: We accessed 135 CFGD reviews (published to January 2015) with 655 included studies; 104 reviews indicated cross-over studies were eligible for inclusion and 52 included at least one cross-over study. We identified 212 unique cross-over studies. We checked the methods sections of reviews to identify how review authors planned to manage cross-over data. We accessed cross-over trial reports, the quality of reporting of the results, and compared them to the data included in the review for the primary outcomes.

Results: Methods sections of reviews varied in detail. Half of the reviews included specific details regarding paired analyses, Elbourne ‘3 stage’ method or first period analysis, the other half made no statement regarding cross-over trials, but referred to the work by Elbourne without giving further details, intended to consult the Cochrane Handbook or a statistician or intended to analyse cross-over data as parallel data.

Full results regarding the quality of reporting within the trial reports and how results were actually included in the reviews will be presented. Conclusions and recommendations at study and review level will also be presented.