11 Systematic reviews and Meta-analysis Flashcards
Q: Compare a systematic review and a meta-analysis.
A: A systematic review aims to answer a defined research question by collecting and summarising empirical evidence and critically appraise relevant research – usually published in the scientific literature - that fits pre-specified eligibility criteria. Looking at more than one study
Meta-analysis refers to statistical techniques used in a systematic review to integrate the results of studies matching the eligibility criteria
Q: Why undertake a systematic review? Problem?
A: provide more generalised conclusions, researchers can conduct a systematic review of the primary studies on a particular research question to provide a comprehensive summary of our knowledge at the time of the review
multiple studies of the same research question often lead to inconsistent or even opposite results = problem
Q: What does assessing quantity and quality of data require?
A: Efficient searching of data (i.e. literature)
Applying formal rules for critical appraisal of data
Q: Systematic approach. Process? Meta-analysis advantage? Systematic review advantage?
A: – Transparent process because of the explicit methods in identifying and rejecting studies.
– A meta-analysis, if appropriate, will increase the power of the study and enhance the precision of estimates of treatment effects, accounting for sample size, and uncertainties.
– Systematic reviews may demonstrate the lack of adequate evidence and thus identify areas where further studies are needed
Q: What do most scientific journals require from systematic reviews?
A: each stage to rigorously follow guidelines or “best practice” recommendations
Q: Describe stage I of a systematic review. Framed around? (4)
A: – Planning the review : The authors need to clearly define the research question to be addressed
– This question is usually framed around the definition of study participants, intervention (exposure), outcomes and study designs of interest
Q: Describe stage II of a systematic review. Requires? Selection? Study quality?
A: – Identification of research : This requires clearly defined search criteria and a thorough search of all published literature (including exhaustive searches of reference lists, conference proceedings and contact with researchers in the field).
– Selection of studies : Inclusion and exclusion criteria should be defined a priori; these are likely to be based on factors such as study design, year, sample size, completeness of information, study quality etc.
– Study quality assessment : Study quality can be assessed against recognised or user-defined criteria, usually to establish whether various biases are likely to exist in the in study (e.g. selection bias, measurement bias, attrition bias/loss to follow-up).
Q: Describe stage III of a systematic review. (3)
A: – Reporting and dissemination – Study details need to be abstracted from each eligible study along with the effect estimate (or details that allow an effect estimate to be calculated)
– These details need to be tabulated in a meaningful way, including, where appropriate, details of populations, interventions/exposure, outcomes and study design, and a summary of the findings
– The last step consists in estimating an overall effect by combining the data
Q: What is specific about meta-analysis when it comes to ‘subjects’? Benefit?
A: More subjects can be included than any single constituent study, producing a more reliable and precise estimate of effect
Q: What are the advantages of a meta-analysis? (3)
A: Produce a more reliable and precise estimate of effect
Explore differences (heterogeneity) between published studies
Identify whether a publication bias is occurring
Q: What happens if the studies are too heterogeneous?
A: it may be inappropriate, even misleading to statistically pool the results from separate studies
Q: What are the limiations of a meta-analysis? (4)
A: Publication bias
Labour intensive
Inconsistency of results (studies differs with respect to, Populations Interventions/exposure, Outcomes, Study design, Clinical differences, Methodological differences, Unknown study characteristics)
Low study quality
Q: What is the most common way of visually summarising the results of a meta-analysis?
A: A Forest plot
This is a graphical representation of the results from each study together with the combined meta-analysis result
Q: What is publication bias?
A: refers to the greater likelihood of research with statistically significant results to be published in the peer-reviewed literature in comparison to those with null or non-significant results
Q: What can failure to include all relevant data in a meta-analysis lead to?
A: the effect of an intervention/exposure is over- or under-estimated
Q: How can heterogeneity be explored?
A: Galbraith (radial) plots
Q: Why may heterogeneity exist?
A: clinical differences, methodological differences or unknown study characteristics
studies may still differ with respect to the exact population, interventions/exposure, outcomes and designs used
Q: What are the limitations in conducting systematic reviews? (3)
A: If there are too few studies matching the eligibility criteria defined, a systematic review might not add much to the field
If the methodological quality of studies is inadequate, then the findings of reviews of this material may also be compromised
Publication bias can distort findings because studies with statistically significant results are more likely to get published
Q: (Guidelines and protocols) What did Cochrane start as?
As a result?
A: organisation involving international researchers and clinicians -> organise medical research information in a systematic way, in order to facilitate the choices that health professionals, patients, policy makers and others face in health interventions according to the principles of evidence-based medicine
set many standards in the field
Q: What is the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)? Focuses on?
A: an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses adopted by many scientific journals
PRISMA focuses on the reporting of reviews evaluating randomized trials, but can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions
Q: What should you ask when appraising a systematic review? (5) Check?
A: Was a clear, pre-defined question addressed?
Was a comprehensive search for relevant research carried out?
Was methodological quality of each study assessed appropriately?
Was heterogeneity (consistency of results) explored?
How credible is the evidence?
(check guidelines for reporting (PRISMA))
Q: What should you ask when appraising a meta-analysis? (5)
A: Was heterogeneity explored?
Was publication bias an issue?
Was it appropriate to pool studies?
Was the appropriate model used to pool effect estimates?
Did different sub groups of studies give similar results?
Q: What do single studies rarely provide?
A: a conclusive, universal answer to a question
Q: What can systematic reviews provide?
A: overview of evidence on a particular topic
Q: What can meta-analyses provide? (3)
A: A single, more precise, estimate of intervention/exposure effect (pooled risk estimate)
A greater understanding of similarities/differences among studies
An assessment of likely publication bias
Q: What can systematic reviews/meta-analyses provide?
A: an evidence-base for clinical decisions
