Article type
Year
Abstract
Background:
The two common problems associated with cross-over trials are carry-over effect and risk of drop-out. Due to these reasons, it is often difficult to extract suitable data from a cross-over trial (Higgins 2009). We undertook this study to see the common problems associated with dentistry and oral health reviews in relation to cross-over trials.
Objectives:
1. To determine the number of published Cochrane dentistry and oral health reviews that include cross-over trials.
2. To assess how many of these cross-over trials have considered sufficient washout period as one of their inclusion criteria.
3. To determine how many reviews have used paired results in meta-analysis.
4. To establish the risk of drop-outs in the included/excluded cross-over trials.
Methods:
We included all 154 published (updated) Cochrane dentistry and oral health reviews. Full texts were downloaded from The Cochrane Library. Titles, inclusion/exclusion criteria, number of cross-over trials included, washout period, drop-outs and data used in meta-analyses were extracted from each review.
Results:
Out of 154 full reviews, 13 had included 49 cross-over trials. In these 13 reviews, eight studies had defined the duration of washout period. Studies in three reviews did not need any washout period and studies in two did not mention washout period. Only five reviews mentioned a minimum washout period as one of their inclusion criteria. Twelve reviews excluded a total of 35 cross-over trials due to a variety of reasons that included insufficient/no washout period (58.3%), pooled data (33.3%) and other issues (8.4%). Meta-analyses were not done in eight reviews. Paired data were combined with parallel group data using generic inverse variance method in two reviews. Two reviews used the data from first half of a study, and one review analysed the cross-over data separately. Risk of drop-out was not a common problem in our study.
Conclusions:
Insufficient washout period and pooled data are the common problems faced by dentistry and oral health reviewers in dealing cross-over studies.
The two common problems associated with cross-over trials are carry-over effect and risk of drop-out. Due to these reasons, it is often difficult to extract suitable data from a cross-over trial (Higgins 2009). We undertook this study to see the common problems associated with dentistry and oral health reviews in relation to cross-over trials.
Objectives:
1. To determine the number of published Cochrane dentistry and oral health reviews that include cross-over trials.
2. To assess how many of these cross-over trials have considered sufficient washout period as one of their inclusion criteria.
3. To determine how many reviews have used paired results in meta-analysis.
4. To establish the risk of drop-outs in the included/excluded cross-over trials.
Methods:
We included all 154 published (updated) Cochrane dentistry and oral health reviews. Full texts were downloaded from The Cochrane Library. Titles, inclusion/exclusion criteria, number of cross-over trials included, washout period, drop-outs and data used in meta-analyses were extracted from each review.
Results:
Out of 154 full reviews, 13 had included 49 cross-over trials. In these 13 reviews, eight studies had defined the duration of washout period. Studies in three reviews did not need any washout period and studies in two did not mention washout period. Only five reviews mentioned a minimum washout period as one of their inclusion criteria. Twelve reviews excluded a total of 35 cross-over trials due to a variety of reasons that included insufficient/no washout period (58.3%), pooled data (33.3%) and other issues (8.4%). Meta-analyses were not done in eight reviews. Paired data were combined with parallel group data using generic inverse variance method in two reviews. Two reviews used the data from first half of a study, and one review analysed the cross-over data separately. Risk of drop-out was not a common problem in our study.
Conclusions:
Insufficient washout period and pooled data are the common problems faced by dentistry and oral health reviewers in dealing cross-over studies.