Presentation on theme: "The Bahrain Branch of the UK Cochrane Centre In Collaboration with Reyada Training & Management Consultancy, Dubai-UAE Cochrane Collaboration and Systematic."— Presentation transcript:
The Bahrain Branch of the UK Cochrane Centre In Collaboration with Reyada Training & Management Consultancy, Dubai-UAE Cochrane Collaboration and Systematic Review Workshop, 20-21 February 2007, Dubai - UAE Dr. Zbys Fedorowicz, Dr. Dunia Al Hashimi, Dr. Ahmed Al Asfoor http://bahrain.cochrane.org/en/index.html http://www.rt.ae W12
Methodological quality of studies to be included in a Systematic Review
Study quality Quality: a multidimensional concept: related to the 1.Design 2.Conduct Internal Validity 3.Analysis of a trial 4.Quality of reporting AND/OR Its clinical relevance i.e. External Validity
The validity of findings in a study External extent to which results provide a correct basis for generalisation to other circumstances (i.e. clinical applicability) Internal extent to which systematic error (bias) is minimised in clinical trials [Selection/Performance/Detection/Attrition]
Assessment of study quality Quality scales vs checklist Validity assessment can be used: - as a threshold for inclusion of studies - as a possible explanation for heterogeneity - in sensitivity analyses - as weights in meta-analysis
Quality scales Jadad scale : Bias in Pain Research Reports: Scaled< 5 What’s missing?
Check lists Cochrane “Risk of Bias” Tables Randomisation Allocation Concealment Blinding of Outcomes Assessment Attrition Everything covered?
Limitations of quality assessment * Inadequate reporting of trials * Lack of empirical evidence * Subjectivity
Meta-analysis * Statistical combination of results, estimating the weighted average of treatment effect. * Investigating heterogeneity across studies: subgroup analysis meta-regression
Variation in results across studies Heterogeneity? (variations/differences) Statistical heterogeneity Clinical heterogeneity Methodological heterogeneity
Clinical heterogeneity might arise from differences between: Participants (e.g. sex, age, severity of illness) Interventions being compared Outcomes collected.
arises through the use of: different trial designs (e.g. parallel, cross-over trials, cluster-randomised trials) and different degrees of control over bias (e.g. risk may differ depending on allocation concealment, blinding, loss to follow up). Methodological heterogeneity
Statistical heterogeneity a consequence of clinical AND methodological heterogeneity
Chance Variations in patients Variations in interventions Different outcome measures Methodological quality Sources of heterogeneity