Article type
Year
Abstract
Background: Increasingly, Cochrane Systematic Reviews draw on nonrandomized study designs when assessing the effectiveness especially of complex interventions. In this context, controlled before-after (CBA) and interrupted time series (ITS) studies receive particular attention due to their recognition by the EPOC Group. There is, however, much confusion as a result of inconsistencies in study design labels and features and in relation to risk of bias.
Objectives: To analyse CBA and ITS studies included in Cochrane Systematic Reviews descriptively in terms of their publication, application and methodological characteristics, focusing on strengths and weaknesses of the two designs.
Methods: We searched the Cochrane Library for systematic reviews including nonrandomized studies from June 2012 to March 2015, updating a methodological study by Ijaz 2014. First, we classified the reviews including CBA or ITS studies according to ten pre-specified types of intervention. Subsequently, and separately for ITS and CBA studies, we purposively selected two reviews from each type of intervention. From each of these reviews, we randomly sampled two CBA or two ITS studies, respectively. Data extraction and analysis were conducted separately by two authors using distinct tools for the two designs.
Results: Our searches identified 126 reviews. From the sample of 40 CBA and 40 ITS studies, we described publication details, field of application (i.e. type and level of intervention), methodological characteristics (i.e. data collection, analysis), and quality assessment. The descriptive analysis yielded notable differences in relation to field of application of the two designs across health policy, health systems, behavioural, environmental, occupational, clinical, pharmaceutical, nutrition, screening and vaccination interventions and uncovered differences in quality of study conduct and reporting.
Conclusions: This study provides further proof of heterogeneity in definitions and study features associated with the 'CBA' and 'ITS' labels. The strengths and weaknesses of the two designs have important consequences for reporting guidelines and quality appraisal tools.
Objectives: To analyse CBA and ITS studies included in Cochrane Systematic Reviews descriptively in terms of their publication, application and methodological characteristics, focusing on strengths and weaknesses of the two designs.
Methods: We searched the Cochrane Library for systematic reviews including nonrandomized studies from June 2012 to March 2015, updating a methodological study by Ijaz 2014. First, we classified the reviews including CBA or ITS studies according to ten pre-specified types of intervention. Subsequently, and separately for ITS and CBA studies, we purposively selected two reviews from each type of intervention. From each of these reviews, we randomly sampled two CBA or two ITS studies, respectively. Data extraction and analysis were conducted separately by two authors using distinct tools for the two designs.
Results: Our searches identified 126 reviews. From the sample of 40 CBA and 40 ITS studies, we described publication details, field of application (i.e. type and level of intervention), methodological characteristics (i.e. data collection, analysis), and quality assessment. The descriptive analysis yielded notable differences in relation to field of application of the two designs across health policy, health systems, behavioural, environmental, occupational, clinical, pharmaceutical, nutrition, screening and vaccination interventions and uncovered differences in quality of study conduct and reporting.
Conclusions: This study provides further proof of heterogeneity in definitions and study features associated with the 'CBA' and 'ITS' labels. The strengths and weaknesses of the two designs have important consequences for reporting guidelines and quality appraisal tools.