4. What are systematic reviews?
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
Systematic Review
• A literature reviewing technique typically used in
evidence-based medicine, but applicable to other
fields of study
• Gathering, critically appraising and summarising all
relevant studies that address a certain research
question
Basis for decision making
Cook et al., 1997
4
5. Why do we need systematic reviews?
Definition
The Cochrane
Collaboration
• The problem:
Too many papers, too little time
The Review
protocol
Conflicting information and
Conducting the recommendations from different
papers
systematic
Conclusions
com
Interpreting
results
www.bvallc.
review
Summaries of all literature on a given topic are needed so that the
evidence is easily and quickly accessible
5
6. Why is it important to be systematic?
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
–
–
–
–
Concise and rigorous literature search
Explicit search strategy
Explicit inclusion and exclusion criteria
Explicit methods for extracting and
summarising data from primary studies
Ensures
reproducibility,
reduces bias
– Overall:
COMPREHENSIVE, EXPLICIT, REPRODUCIBLE, RATIONAL
6
7. Systematic vs. traditional reviews
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
Traditional
Systematic
Research
question
Broad
Specific
Search strategy,
data collection
and
interpretation
Informal, subjective,
not explicit
Explicit, clear, with
rationale
Critical appraisal May or may not take
Systematic using
of included
place, not using specific standardised tools
studies
tools
Cipriani and Geddes, 2003
7
8. Different forms of literature reviews
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Literature reviews
Systematic
reviews
Metaanalyses
Traditional
reviews
Interpreting
results
Conclusions
8
9. What is a meta-analysis?
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
= “the use of statistical techniques to integrate and
summarise the results of included studies”
• Combining information from several studies
larger sample size
higher precision
higher statistical power (= the probability that the
statistical test will detect an effect that is really there)
Conclusions
Liberati et al., 2009
9
10. What is a meta-analysis?
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
• Whether you can conduct a meta-analysis depends
on:
– No. of available studies
– Variability of methods and outcome measures
• If a meta-analysis is not possible, a
narrative/qualitative systematic review can be
conducted
Conclusions
10
11. Who can conduct a systematic review?
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• The review team should have skills in
–
–
–
–
–
Systematic review methods
Information retrieval
The relevant topic area
Statistics
Qualitative research methods
• It is good practice to have at least 2 researchers
involved minimise bias and error
11
13. Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
= an international network
• named after Archie Cochrane (1909-1988), a British
epidemiologist, who advocated evidence-based
medicine
• Aim: Provide resources to enable well-informed
decisions about health care
• http://www.cochrane.org/
13
14. Cochrane reviews
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
= Systematic reviews and meta-analyses published by the
Cochrane Collaboration in the Cochrane Library
• Specific methods, structure and format: Cochrane
Handbook for Systematic Reviews of Interventions
• “internationally recognised as the highest standard in
evidence-based health care”
• Existing Cochrane Reviews are updated regularly as
new information becomes available
Can result in changed conclusions
14
16. Cochrane reviews in Manchester
Definition
• Cochrane groups with editorial base in Manchester
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
• Cochrane Oral Health Group, School of Dentistry, The
University of Manchester
• The Cochrane Bone, Joint and Muscle Trauma Group
(BJMTG)
Interpreting
results
Conclusions
16
18. Review Protocol
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• Describes the methods to be used in the review
–
–
–
–
–
–
–
–
–
Background
Review question
Inclusion/Exclusion criteria
Search strategy
Study selection
Quality assessment
Data extraction
Data synthesis
Plans for dissemination
• Specifying the methods in advance reduces the risk of bias
• If modifications are required, they should be documented
and justified
18
19. Background
Definition
The Cochrane
Collaboration
• Key contextual factors relevant to the review question
• Explain why the review is required
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
19
20. Background: CS-related example
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
Example Kitchenham et al. (2007): “A Systematic Review
of Cross- vs. Within-Company Cost Estimation
Studies.”
• Two different types of cost estimation models
• Within-company models developed using one company’s
data
• Cross-company models developed using datasets from
several companies
• Several studies have compared prediction accuracies with
contradictory results
• Important for small companies who do not have their own
project data
Systematic review to determine factors that influence the
outcome of studies comparing within and cross-company models
20
21. Inclusion criteria
Definition
The Cochrane
Collaboration
The Review
protocol
• Language: The ideal is to include all available relevant
evidence, but this often not feasible Language bias
• Publication type/status
– Full papers in peer-reviewed journals
Conducting the
systematic
review
Interpreting
results
Conclusions
“Publication bias”: When studies with significant
results are more likely to get published
–
–
–
–
–
–
Contact authors
Ongoing studies partially published as conference abstracts
Reports and discussion papers
Book chapters
Theses
…
21
22. Inclusion criteria
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• Use the “PICOS” elements:
Population: Patients or Users (disease, age, gender,
disability), software, type of technology, websites …
Interventions: Type, main features …, e.g. assistive
technology for disabled users…
Comparison: No treatment, treatment as usual;
between or within organisations …
Use this
to define
your
question
Outcomes: e.g. survival, disease remission,
interactions with the keyboard, commands
executed, …
Study design: Randomised controlled trials,
cohort studies, case-control studies…
22
23. Review question
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
• Clear, as specific as possible
• Example 1: Are psychological interventions effective in
reducing chronic headache in children and
adolescents?
• Example 2: Are cross-company models significantly
worse than within-company estimation models for
predicting effort for software/web projects?
Conclusions
23
24. Building the search strategy
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
1. Describe all relevant PICOS elements (you might not
want to include all!)
2. Organise them into concepts
3. Find all related words and synonyms
4. Search all synonyms for one concept with “OR”
5. Combine all concepts with “AND”
Interpreting
results
Conclusions
24
25. Search: Health-related example
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
Example: Are psychological interventions effective in
reducing chronic headache in children and adolescents?
Population
1. Concept: “Children and adolescents”
Child* OR adolescen* OR juvenile OR paediatric
2. Concept: “Headache”
Headache OR migraine OR tension headache
Interventions
3. Concept: “Psychological interventions”
psycholog* OR psychotherapy OR biofeedback
OR relaxation OR cognitive OR behavio#ral
1. AND 2. AND 3.
25
26. Search: CS-related example
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• Kitchenham et al. (2007). A Systematic Review of Cross- vs.
Within-Company Cost Estimation Studies.
1. Population: software OR application OR product OR Web OR
WWW OR Internet OR World-Wide Web OR project OR
development
2. Intervention: cross company OR cross organisation OR cross
organization OR multiple-organizational OR multipleorganisational model OR modeling OR modelling effort OR cost
OR resource estimation OR prediction OR assessment
3. Comparison: within-organisation OR within-organization OR
within-organizational OR within-organisational OR single
company OR single organisation
4. Outcome: Accuracy OR Mean Magnitude Relative Error
• 1. AND 2. AND 3. AND 4.
26
28. Conducting a literature search
Definition
The Cochrane
Collaboration
Search electronic databases, e.g. ACM Digital Library, CiteSeer,
INSPEC, …
The Review
protocol
Conducting the
systematic
review
Visually scan reference lists from
identified studies
Handsearch key journals and
conference proceedings
Interpreting
results
Conclusions
Contact study authors, experts, manufacturers, other
organisations …
…
28
29. The Review
protocol
Conducting the
systematic
review
Interpreting
results
# of records after duplicates
removed
# of records screened (title,
abstracts)
# of records excluded
# of full-text articles assessed
for eligibility
# of full-text articles
excluded, with reasons
included
Conclusions
# of records identified
through other sources
screening
The Cochrane
Collaboration
# records identified through
database screening
eligibility
Definition
identification
Conducting a literature search
# of studies included in data
synthesis
Liberati et al., 2009: The PRISMA statement for reporting systematic reviews
29
30. Quality assessment
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• A review should be based on the best quality evidence
available
• The quality of the included studies will impact on the
reliability of the results of the review
• Useful tools for quality assessment
– CASP tools (Critical Appraisal Skills Programme), e.g.
CASP checklist for randomised controlled trials
– JADAD scale
– …
30
31. Quality assessment: CS
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
Kitchenham et al. (2007)
• 6 questions to assess the quality of included studies,
developed by the researchers themselves
• Examples:
– Is the analysis process description complete?
– Is it clear how accuracy was measured?
– Were all model construction methods fully defined
(tools and methods used)?
31
33. Data synthesis
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
• If a meta-analysis is possible, data can be summed up
statistically using quantitative methods
• If not, data can be synthesised narratively
• Narrative data synthesis usually ocurrs in form of
table(s) and textual description
Conclusions
33
34. Narrative data synthesis: Health-related example
Author, dat
e and
location
Participant
demographics,
attrition
Intervention
length,
content and
groups
Measures
and followup
Reported
results
Author’s
conclucions
Segatto et
al., 2010.
Brazil
N= 175
90.3% male
Age: 21.8 (2.6)
16 – 25 years
Mostly Caucasian
(71%)
Patients in
emergency room
Attrition: 14,9% ,
no differences
btw. completers
and dropouts
found
Motivational
Interview (MI):
person-centred
techniques, also
included EB (45
min.)
Educational
brochure (EB): 3
page
informative
general
guidance on
risks of alcohol
(5 min.)
Alcohol
Consumption
Questionnaire
(ACQ), Rutgers
Alcohol
Problems Index
(RAPI), Alcohol
Consumption
Risk
Questionnaire
(ACRQ),
Measured at
baseline and 3
months
Time effect for:
days of alcohol
use, days with
moderate use,
days
with heavy use,
negative
consequences,
being in action
stage
No sig.
differences in
long-term
change in riskperception
No group x time
effects
MI alone not
able to promote
sig. and lasting
changes
Limitations:
brief
interventions
usually target
risk populations
at an early
stage, too short
observation
time
…
…
…
…
…
…
34
36. Interpreting results
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• Was there consensus across all studies?
• Where did studies differ? What might be the reason?
Did these studies differ in participant populations,
methods/measures used …?
• Did it make sense to pool the results?
(heterogeneity/homogeneity)
• Discuss the quality of the included studies: Can the
results of the review be valid?
• Discuss possible sources of bias: Publication bias,
language bias…
36
38. Conclusions
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
• Systematic Reviewing is designed to ensure a
comprehensive, reproducible and critical review of all
the available literature on a given topic
• Not all techniques shown here will be equally
applicable to CS
Interpreting
results
Conclusions
• Other methods may be legitimate as long as they are
stated explicitly and a rationale is provided
38
39. Thanks for listening.
Any questions?
Julia Mueller
julia.mueller@postgrad.manchester.ac.uk
http://jnmueller.wordpress.com/
School of Computer Science,
LF1 Kilburn Building,
Oxford Road, MANCHESTER,
M13 9PL, UK
39
40. References
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
2009. Systematic Reviews: CRD's guidance for undertaking
reviews in health care. CRD, University of York.
CIPRIANI, A. & GEDDES, J. 2003. Comparison of systematic and
narrative reviews: the example of the atypical
antipsychotics. Epidemiol Psichiatr Soc, 12, 146-53.
COOK, D. J., MULROW, C. D. & HAYNES, R. B. 1997. Systematic
reviews: synthesis of best evidence for clinical decisions.
Ann Intern Med, 126, 376-80.
LIBERATI, A., ALTMAN, D. G., TETZLAFF, J., MULROW, C.,
GOTZSCHE, P. C., IOANNIDIS, J. P., CLARKE, M., DEVEREAUX,
P. J., KLEIJNEN, J. & MOHER, D. 2009. The PRISMA
statement for reporting systematic reviews and metaanalyses of studies that evaluate healthcare interventions:
explanation and elaboration. BMJ, 339, b2700.
40
41. References
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
Interpreting
results
Conclusions
• Here’s an example of a well-conducted systematic
review and meta-analysis:
COVENTRY, P. A. & HIND, D. 2007. Comprehensive
pulmonary rehabilitation for anxiety and depression in
adults with chronic obstructive pulmonary disease:
Systematic review and meta-analysis. J Psychosom
Res, 63, 551-65.
Cochrane Handbook for systematic reviews for
interventions: http://handbook.cochrane.org/
41
42. References
Definition
The Cochrane
Collaboration
The Review
protocol
Conducting the
systematic
review
• This is a systematic review in the area of CS:
Kitchenham, B., Mendes, E., Travassos, G.H. (2007) A
Systematic Review of Cross- vs. Within-Company Cost
Estimation Studies, IEEE Trans on SE, 33 (5), pp 316329.
• Guidelines for performing Systematic Literature
Reviews in Software Engineering
Interpreting
results
Conclusions
42