Fiona Beyer on behalf of the Evidence Synthesis Team Institute of Health amp Society fionabeyernclacuk Aims of this session What is a systematic review How to formulate an appropriate review question ID: 586737
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Slide1
Introduction to Systematic Reviews
Fiona Beyer on behalf of the Evidence Synthesis Team
Institute of Health & Society
fiona.beyer@ncl.ac.ukSlide2
Aims of this session….
What is a systematic review?
How to formulate an appropriate review question?
Why and how to write a protocol?
How to find relevant studies?How to extract appropriate data? How to critically appraise studies? Introduction to synthesis
BRIEF
introduction and signposting!Slide3
What is a systematic review?
SYSTEMATIC
:
Done or acting according to a fixed plan or system: methodical
REVIEW: A critical appraisal of a book, play or other workSlide4
“A
systematic review
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 collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question. It uses explicit, systematic methods that are selected with a view to
minimizing bias
, thus providing more reliable findings from which conclusions can be drawn and decisions made (Antman 1992, Oxman 1993)
What is a systematic review?Slide5
Why
use systematic reviews?
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 trialsSlide6
Facilitate
rational decision making
Health care providers, researchers and policy makers are inundated with unmanageable amounts of information
Over 20 million citations in PubMed
Approx. 75 to 100 RCTs published dailyUsually 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
Why
use systematic reviews?Slide7
Why not
traditional
reviews?
‘Traditional’ reviews
Systematic reviewsUnclear how included studies were selectedProtocol specifies exact research question/inclusion criteriaBased on incomplete set of studiesComprehensive search to find all relevant studiesMay not consider quality of included studiesStandardised critical appraisal across included studiesUnclear
how conclusions follow from included studies
Methods transparent and reproducibleSlide8
Hierarchy of evidenceSlide9
Who undertakes systematic reviews?
Cochrane/Campbell Collaboration
NICE/Regulatory bodies
Health Technology Assessment
Academics/researchers/clinicians
MSc/PhD studentsSlide10
Multidisciplinary teams
Clinicians
Health services researchers
Information scientists
Statisticians Health economists Patient and public involvement
Who undertakes systematic reviews?Slide11
Systematic Reviews -
the
process (1)
Define review question
– very precisely; in partnership with commissioners, clinicians, patients (as appropriate)Develop protocol – provides transparency; defines exact inclusion criteria and methodsIdentify relevant studies – usually comprehensive search across multiple bibliographic databases plus reference checkingAssess eligibility – careful matching of studies against inclusion criteriaSlide12
Systematic Reviews -
the
process (2)
Extract
relevant data – only what is required to answer the questionCritically appraise studies – use a published tool to compare methodological features across studiesSynthesise appropriately – depending on type of question and study designs quantitative or qualitative synthesis
Disseminate
to appropriate audience – full transparent write-up plus as appropriate short report to funder, journal article, patient leaflet… Slide13
Formulating the review questionSlide14
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 findingsSlide15
Quick Activity
Discuss a very broad question and how you might narrow it? (10 mins)
Discuss the potential limitations of your review questions
If time and resource were not a limitation – consider how useful would the answer to your review question be?Slide16
Current guidance
a clear and concise statement of a review's objectives (or questions) is critical and should begin with a precise statement of the primary objective, including the interventions reviewed and the targeted problem; ideally, this would be presented in a single sentence
Cochrane & PRISMA StatmentSlide17
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
].” Slide18
Formulating review question
Determining the scope is a decision dependent upon multiple factors:
Perspectives regarding a question’s relevance and potential impact;
Supporting theoretical, biologic and epidemiological information;
The potential generalizability and validity of answers to the questions;
Available resources;
The wider literature base – has a recent high-quality SR been conducted?Slide19
Formulating review question
Often dealing with complex interventions
Might be a need to develop working definitions of the intervention of interest
Several options on how to do this (pragmatic real world v theoretical, logic models, etc.)
Use content experts outside the review team to ensure that the resulting definitions are likely to be robust and meaningful
Need to carefully consider appropriate study design which will answer your particular questionSlide20
Formulating review question
Advantages
Disadvantages
Broad
questionComprehensive summary of all evidenceMay ‘lump’ interventions that are heterogeneous – apples/ pearsFindings are likely to be generalisableMay be a lot of studies to manage (difficult for narrative synthesis)Narrow questionMore discrete and manageable inclusion criteriaMay be too few studies to provide meaningful result (although this can be useful evidence of ‘gap’)Less heterogeneity
May
not be generalizable at allSlide21
Formulating review
question: tools (1)
PICO is for effectiveness questions which usually use controlled trials
Glasziou et al, 2003Slide22
1. Setting
what is the context of the question?
e.g. European
countries
2. Perspective who are the users/potential users of the outcomes? e.g. chronically ill3. Intervention what is being done to them? e.g. increased cost-sharing4. Comparison what are the alternatives? e.g. no increase5. 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)Slide23
Sample a description of 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)Slide24
Any questions??Slide25
Developing the protocolSlide26
Developing protocol
A protocol 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 reviewsSlide27
One of the features that distinguish a systematic review from a traditional review is the pre-specification of criteria and methods
W
hat 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 protocolSlide28
PROSPERO – CRD initiative
Search for ongoing reviews
Register planned review online (& update as work progresses)
Avoids duplication of reviewsSlide29
Finding eligible studiesSlide30
Searching for eligible studies
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)Slide31
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 studiesSlide32
Searching for eligible studies
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.)Slide33
Where to searchElectronic 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 areasCheck existing systematic reviews in a similar area for ideasLook 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 studiesSlide34
Boolean operatorsSlide35
Select potentially eligible 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 inclusionRequires judgement (>1 reviewer)Check reviewer agreement (3rd review to resolve)Use a selection form to ensure consistency and record decisionsSelecting included studiesSlide36
Any questions??Slide37
Data
ExtractionSlide38
Data
Extraction (1)
Pilot a data extraction form
See options later
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 toolSlide39
What effect measures 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)Slide40
Extract
sufficient
information:
to describe studies
to allow you to undertake the planned analysisso you do not need to return to the full text papersBut not too muchDon’t waste time extracting ‘nice to have’ but unnecessary detail
Data
Extraction (3)
REMEMBER YOUR PROTOCOL
IT
IS YOUR ROADMAP, FOLLOW IT!Slide41
There is a wide selection of software to choose
from
Consider:
What
are you are familiar with?What package best suits your data?How many included studies do you have?
Data
Extraction (4)Slide42
Software Options
Word
Excel
Access
EPPI reviewer
COVIDENCE
REVMAN
????Slide43
Consistency/Standardisation
Data extractors need to collect and interpret data in a standard way
Essential
>one reviewer is extracting
data
Independent
piloting of data extraction forms – always one standardised form
Regular
discussion of progress/disagreements
Regular comparison of data extraction – don’t wait till the endSlide44
Efficient data extraction
Once data extraction is complete you may need to
:
Sort/search your data
Filter
data
Calculate frequencies
Transform data (e.g. SE to SD)
Categorising/coding data will make these tasks easier:
Needs to be implemented with consistency by the whole team Slide45
Things to consider
You
may
need to update the form, or have more than one
form
Any changes need to be agreed and made consistently
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
sameSlide46
Things to consider
You
may
need to update the form, or have more than one
form
Any changes need to be agreed and made consistently
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
sameSlide47
Any questions??Slide48
Critical AppraisalSlide49
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 inferencesSlide50
Critical
Appraisal
Quantitative studies
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)Slide51
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
AppraisalSlide52
CASP appraisal checklist
Clear aims of research (goals, why it is important, relevance)
Appropriate methodology
Sampling strategy
Data collection
Relationship between researcher and participants
Ethical issues
Data analysis
8.
Findings
9
.
Value of research (context dependent) Slide53
Any questions??Slide54
Data synthesisSlide55
Data Synthesis
Building up; putting together; making a whole out of the parts; the combination of separate elements of thought into a whole; reasoning from principles to a conclusionSlide56
Data Synthesis
Results from different studies types need to be
synthesised
appropriately
Quantitative data meta-analysis (if enough homogeneity in interventions/ outcomes/ study designs) AND/ORnarrative synthesisQualitative dataVarious methods depending on review purpose, e.g. meta-ethnography, thematic synthesis Slide57
Meta-analysis/forest plotSlide58
Heterogeneity
Differences
Methodological heterogeneity: study design/ 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)!Slide59
Narrative synthesis
Instead of/alongside meta-analysisPotential bias in presentation
Can be more difficult to provide a take home messageSlide60
Narrative synthesis - tools
Partly informed by methodological work in qualitative synthesis
Tabulation
Groupings and clusters
Vote counting as a descriptive toolExamination of moderator variables (elements of e.g. setting, population)Slide61
Qualitative synthesis
Some qualitative 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 evidenceSlide62
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 guidelinesSlide63
Be organised!!!
Maintain an audit trail; keep good records of all decisionsSlide64
Version control
Dates – YYYYMMDDVersion numbering v0.1 = first draft
v1.0 = final version
v1.1 = minor amendments to final version
v2.0 = major revisionAvoid using draft, draft 1, final , etc.Clear naming conventionE.g. Date_project_title 20/11_Autism HTA_resultsv1.2.docSlide65
Gantt chartsSlide66
Other help available
FMS Systematic review group
Informal monthly session where methods are discussed and issues can be raised (Baddiley-Clark building)
fiona.beyer@ncl.ac.uk
or jenni.hislop@ncl.ac.ukMSc in Public Health and Health Services Research (~October 2017)10 credit module ‘Introduction to systematic reviewing and critical appraisal’pghealth@newcastle.ac.ukSlide67
Any questions??Slide68
Thanks for your attention!
Contact details:
Fiona Beyer
Institute
of Health & Society fiona.beyer@ncl.ac.uk Slide69
ReferencesAntman, E. M. et al (1992) A
comparison of results of meta-analyses of randomized control trials and recommendations of clinical experts. JAMA 268:240-248
Booth
, A. and Brice, A. (2004), “Appraising the evidence”, in Booth, A. and Brice, A.
(eds), Evidence Based Practice for Information Professionals, Facet Publishing, London, pp. 104-18.CASP Critical appraisal tools http://www.casp-uk.net/checklists Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011], (2011) Higgins, J.P.T. and Green, S. (eds.) The Cochrane Collaboration. http://handbook.cochrane.org/Cooke A, Smith D, & Booth A. "Beyond PICO: the SPIDER tool for qualitative evidence synthesis." Qualitative Health Research 22.10 (2012): 1435-1443.Covidence https://www.covidence.org/ Centre for Reviews and Dissemination (2009) Systematic Reviews: CRD's guidance for undertaking systematic reviews in health care. www.york.ac.uk/inst/crd/pdf/Systematic_Reviews.pdf Equator network (reporting guidelines) https://www.equator-network.org/reporting-guidelines/ Glasziou P & Del Mar C. Evidence-based medicine workbook: finding and applying the best evidence to improve patient care. University of Queensland, 2003.Higgins, J.P.T. et al (2016) 'A revised tool for assessing risk of bias in randomized trials', in Chandler, J., McKenzie, J., Boutron, I. and Welch, V. (eds.) Cochrane Database of Systematic Reviews.Klassen et al. Guides for reading and interpreting systematic reviews. Arch Pediatr Adolesc Med 1998;152:700-704Moher,
D. et al (2009
) 'Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement',
Annals of Internal Medicine, 151(4), pp. 264-269
.Oxman AD, Guyatt
GH.
(1993) The
science of reviewing research.
Annals of the New York Academy of
Sciences
703: 125-13
Prospero
https://www.crd.york.ac.uk/PROSPERO
/
Whiting,
P.F. et al
(2006) 'Evaluation of QUADAS, a tool for the quality assessment of diagnostic accuracy studies',
Medical Research Methodology, 6(9), p. 8
.
Whiting,
P. et al
(2016) 'ROBIS: A new tool to assess risk of bias in systematic reviews was developed',
Journal of Clinical Epidemiology, 69, pp. 225-234.