Download to read offline
![Current guidance- Cochrane
• “To assess the effects of [intervention or
comparison] for [health problem] in [types of
people, disease or problem, and setting if
specified].”](https://image.slidesharecdn.com/srandma-250509130836-1803ec6e/75/Systematic-review-and-meta-analysis-pptx-8-2048.jpg)
More Related Content
Similar to Systematic review and meta analysis.pptx
Systematic review and meta analysis.pptx
- 1. What is asystematic review? SYSTEMATIC: Done or acting according to a fixed plan or system: methodical REVIEW: A critical appraisal of a book or other work
- 2. • “A systematicreview is a review in which there is a comprehensive search for relevant studies on a specific topic, and those identified are then appraised and synthesized according to a predetermined and explicit method.” (Klassen 1998) • A systematic review attempts to collect all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. • Providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993) What is a systematic review?
- 3. Why use systematicreviews? • Minimise the impact of bias/errors • Can help to end confusion • Highlight where there is not sufficient evidence • Combining findings from different studies can highlight new findings • Can mitigate the need for further trials • Health care providers, researchers and policy makers are flooded with unmanageable amounts of information – Over 20 million citations in PubMed – Approx. 75 to 100 RCTs published daily – Usually impossible to consider all relevant individual primary research studies in a decision making context Enable practitioners to keep up to date and practice evidence-based medicine Facilitate rational decision making
- 4.
- 5. Systematic Reviews Process •Define review question • Develop protocol • Identify relevant studies • Assess eligibility • Extract relevant data • Critically appraise • Synthesise • Disseminate
- 6.
- 7. Formulating review question •Questions may be broad or narrow • Well-formulated questions will guide many aspects of the review process – Searching strategy – Inclusion/exclusion criteria – Data extraction – Choice of synthesis method – Presentation/dissemination of findings
- 8. Current guidance- Cochrane •“To assess the effects of [intervention or comparison] for [health problem] in [types of people, disease or problem, and setting if specified].”
- 9. Formulating review question: tools(1) PICO is for effectiveness questions which usually use controlled trials Glasziou et al, 2003
- 10. 1. Setting whatis the context of the question? e.g. European countries 2. Perspective who are the users/potential users of the outcomes? e.g. chronically ill 3. Intervention what is being done to them? e.g. increased cost-sharing 4. Comparison what are the alternatives? e.g. no increase 5. Evaluation how will you measure if the intervention is successful? e.g. access to health services SPICE is designed for questions around public health interventions Booth 2004 Formulating review question: tools (2)
- 11. Sample a descriptionof what is likely to be a smaller group of participants Phenomenon (of) may not be an intervention or exposure Interest Design details of the design will help to make decisions about the robustness of the research Evaluation what are you measuring? Research type qualitative, mixed methods? Cooke et al 2006 Formulating review question: tools (3)
- 12.
- 13. Developing protocol • Aprotocol is an essential component of the systematic review process • Helps to ensure careful a priori planning of whole process – Consistency – Transparency – Integrity • Journals often require a protocol registration number before publishing systematic reviews
- 14. • One ofthe features that distinguish a systematic review from a traditional review is the pre-specification of criteria and methods – What studies will be included and excluded? (use previous question formulation tools) – How (exactly) will each stage be conducted? (search strategy – consult librarian, study selection, critical appraisal, synthesis method – consult statistician) – What are the primary and secondary outcomes of interest? Developing protocol
- 15. PROSPERO – CRD(Centerfor Review and Dissemination) initiative • Search for ongoing reviews • Register planned review online (& update as work progresses) • Avoids duplication of reviews
- 16.
- 17. Searching for eligiblestudies • Can use the same tools to help define search as for question formulation (PICO, SPICE, SPIDER) – Use only the items needed to define search (usually at minimum population and intervention/phenomenon of interest), sometimes outcomes – Consult information specialist or librarian for advice (the search is the first potential major source of bias in your review)
- 18. • Thesaurus headings(e.g. MeSH in MEDLINE) • Controlled vocabulary thesaurus used for indexing articles • Standardised search terms regardless of how author has described the study • Each database has a different thesaurus – must translate Searching for eligible studies
- 19. Searching for eligiblestudies • Keywords • Also search title and abstract fields in case of imprecise or non existent indexing • Need synonyms and truncation to search word stems (e.g. child* retrieves child, children, childless, childbirth, etc.) • Effect of substance use on adherence to ART among adulation with HIV in Ethiopia Substance (alcohol, chat/khat, smoking, IV drug) Adherence (compliance) ART (chronic care) Ethiopia
- 20. • Where tosearch • Electronic databases according to the topic area: MEDLINE, EMBASE, Cochrane databases, PsycInfo, etc. • Grey literature, dissertations, theses, conference proceedings, national bodies (NICE, HTA), clinical trial database (www.clincialtrails.gov/) • University library web pages give advice about databases available in different topic areas • Check existing systematic reviews in a similar area for ideas • Look at the databases own guidance for searching they vary! • Download results to reference management software (e.g. University supports Endnote, alternatively Mendeley) Searching for eligible studies
- 21.
- 22. • Select potentiallyeligible abstracts (in Endnote) • Assess titles/abstracts against your predetermined inclusion/exclusion criteria, use groups or custom fields to record • Retrieve full text articles of initial selections • Assess full text for inclusion • Requires judgement (>1 reviewer) • Check reviewer agreement (3rd review to resolve) • Use a selection form to ensure consistency and record decisions Selecting included studies
- 23.
- 24. Data Extraction (1) •Collect the following information: – Citation details to identify the study – Characteristics of population/intervention – Outcomes at baseline and follow-up – Methodological details according to chosen critical appraisal tool
- 25. • What effectmeasures do you want to calculate? – What data do you need to do this? • How are you planning to group studies for the analysis? – By intervention, study design?? • What information do you need to extract to enable you to organise and analyse the way you want? Data Extraction (2)
- 26. • Extract sufficientinformation: – to describe studies – to allow you to undertake the planned analysis – so you do not need to return to the full text papers • But not too much – Don’t waste time extracting ‘nice to have’ but unnecessary detail Data Extraction (3) REMEMBER YOUR PROTOCOL IT IS YOUR ROADMAP, FOLLOW IT!
- 27. Things to consider •Are you including more than one study design? – You may need separate forms for each study design – However, you are still answering the same question, so make sure the core information extracted is the same • Have one or a few studies reported data differently from the others? Will the data still be useful? Should you include it? Make sure the core information extracted is the same
- 28.
- 29. Critical Appraisal • Why- what are we trying to achieve? • Not all published and unpublished literature is rigorous! – being in a journal doesn’t mean it is good • Quality may be used as an explanation for differences in study results or to guide interpretation of findings, strength of inferences
- 30. Critical Appraisal • Quantitativestudies – Internal validity – Bias: selection; performance; detection; attrition; reporting – External validity • Better to use domain based assessment not numerical scores – Cochrane Risk of Bias 2.0 – RCTs (Higgins 2016) – QUADAS 2 – diagnostic accuracy (Whiting 2006) – ROBIS for systematic reviews (Whiting 2016)
- 31. • Qualitative studies •Three broad categories – Rigour: has a thorough and appropriate approach been applied to key research methods in the study? – Credibility: are the findings well presented and meaningful? – Relevance: how useful are the findings to you and your organisation? Critical Appraisal
- 32. CASP appraisal checklist 1.Clear aims of research (goals, why it is important, relevance) 2. Appropriate methodology 3. Sampling strategy 4. Data collection 5. Relationship between researcher and participants 6. Ethical issues 7. Data analysis 8. Findings 9. Value of research (context dependent)
- 33.
- 34.
- 35. Data Synthesis • Buildingup; putting together; making a whole out of the parts; the combination of separate elements of thought into a whole; reasoning from principles to a conclusion
- 36. Data Synthesis • Resultsfrom different studies types need to be synthesised appropriately • Quantitative data • meta-analysis (if enough homogeneity in interventions/ outcomes/ study designs) AND/OR • narrative synthesis • Qualitative data • Various methods depending on review purpose, e.g. meta-ethnography, thematic synthesis
- 37.
- 38. Heterogeneity Differences Methodological heterogeneity: studydesign/ biases (Statistical) heterogeneity: intervention effects are more different than expected due to chance Clinical heterogeneity: variability in participants or interventions Shouldn’t statistically pool if too much heterogeneity ask for advice (early)!
- 39. Narrative synthesis • Insteadof/alongside meta-analysis • Potential bias in presentation • Can be more difficult to provide a take home message
- 40. Qualitative synthesis • Somequalitative synthesis methods are based on those used in primary qualitative research • Qualitative synthesis generates theories and explanations from analysis of textual data (rather than effect size) • Critical appraisal is not used for discarding ‘unfit’ studies but still important for understanding weight of evidence
- 41. Reporting your review •Ensure you follow guidance for reporting your protocol (PRISMA-P) and systematic review • PRISMA for meta-analysis of RCTs, MOOSE for observational studies, ENTREQ for qualitative syntheses • See Equator network for full set of reporting guidelines