Systematic Review

Assist. Prof. Petra Povalej Brzan, Phd

Faculty of Health Sciences

University of Maribor

petra.povalej@um.si

Outline

Systematic Review

• What is a systematic review paper?

• Difference between systematic review and ordinary literature search

• Writining a systematic review

What is a systematic review?

Systematic Review

- A specific type of review which is folowing a specific standard:

Q: WHY STRICT

STANDARDS???

A: Validity of conclusions

generated by systematic reviews

depends on the methodological

validity of conducted systematic

review.

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A Systematic Review

Systematic Review

• Is a separate scientific study of all availableevidence on a choosen topic.

• Is completely depended on used methodology => the need for folowingspecific standards!

• Has a valid study design!

Systematic Review

A Systematic Review ProcessDefine the question

Create the protocolAssemble the team

Conduct the search

Select studies per protocol

Assess the quality of studies

per protocol

Extract and combine data

from studies

Analyze and present the

results

Interpret results

Write the report

Publish the report

Ordinary Literature Search

Systematic Review

1. Do a little bit of a searching:• usually in some well known journals

• from some well known authors

• articles that tend to support your arguments

2. Sinthesize the articles for the review

A search for Systematic Review

Systematic Review

• Most exhaustive literature search possible:• Published and unpublished literature

• Not limited on specific geographical region or language

• Search on all applicable domains

• Articles that are not methodologically sound MUST be excluded from thesystematic review.

• May require hand search for relevant articles and contacting authors to obtain fulltext articles

• BE AWARE: Results of systematic review may confirm our initialhypothesis or not!

• CHOOSE A STANDARD

• All reviews should be systematicaly depended on what type of reviewyou are writing – a chosen standard (may not need to take every step)!

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A Goal of Systematic Review

Systematic Review

COMPREHENSIVE METHODOLOGICAL

TRANSPARENT

REPRODUCABLE

UNBIASED

REAL

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Step 1: Define the Question

Systematic Review

• What is your question that you are trying to answer with systematicreview?

• What are the key consepts of your question?

ASK PICO!

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The PICO or PICOT model

Systematic Review

• Patient / Population / Problem (among ____)

• Intervention / Exposure (does ____)

• Comparison (versus ____)

• Outcome (affect ____)

• Time (when ____)

• P: Who are the patients we are interested in?

• I: What intervention are we interested in knowing more about?

• C: Is there a comparison to be evaluatedagainst the intervention? (optional)

• O: What is the desired outcome to be evaluated?

• T: What is the time frame? (optional)

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Systematic Review

For persons entering a hospital, is rubbing hands with alcohol based

solution, more effective as standard hand washing with antiseptic soap forreducing risk of hand contamination.

• P: Who are the patients we are interested in?

• I: What intervention are we interested in knowing more about?

• C: Is there a comparison to be evaluated against the intervention? (optional)

• O: What is the desired outcome to be evaluated?

• T: What is the time frame? (optional)

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Systematic Review

• P: Who are the patients we are interested in?

• Persons entering a hospital

• I: What intervention are we interested in knowing more about?

• Rubbing hands with alcohol based solution

• C: Is there a comparison to be evaluated against the intervention? (optional)

• Washing hands with antiseptic soap

• O: What is the desired outcome to be evaluated?

• Reducing risk of hand contamination

• T: What is the time frame? (optional)

• Not included

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After We have a Question…

Systematic Review

• Check if you question has already beenanswered in the past!

• Assemble a team that will work on thesystematic review.

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Step 2: Create a Review ProtocolSystematic Review

• Discussion of the review question

• Description of the search process

• Choose relevant resources (databases, journals,…)

• Choose relevant keywords

• Definition of the criteria for theinclusion and exclusion of studies(eligibility criteria)

• Definition of the process for assessingthe quality of studies

• Data extraction and synthesisprocedures

• Record keeping practice

• Timetable

FOLOW SPECIFIC TEMPLATE OF A CHOOSEN STANDARD (Chochran, PRISMA, CRD,…)!

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Has anyone done that review before?

Systematic Review

• Search for systematicreviews in digital libraires:

• PubMed

• The Cochrane Library

• …

• Use synonims andcontrolled vocabulary

• „pressure ulcer“

• „pressure sore“

• „bed sore“,…

• PROSPERO – Internationalprospective register ofsystematic reviews

• Evaluating existingsystematic reviews if theyexist.

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Systematic Review

• Try large databases relevant to your topic:• Example: PubMed – for biomedical topics…

• Good insight to the number of existing studies

• Find key studies and key autors

• Use citation analysis in order to find other interesting studies

• Find out good descriptions of your subject

• Develop a list of good search terms (keywords)

• Construct good search queres using all defined synonimes

Are there enough primary studies to conduct the review?

„pressure ulcer“ or „pressure sore“ or „bed

sore“ and …

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Where to search?

Systematic Review

• Core medical databases:

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Step 3: Conducting SearchSystematic Review

• Databases relevant to the problem domain:• CINAHL Plus with Full Text

• National Guideline Clearinghouse

• PubMed

• MEDLINE

• Cochrane Collection Plus

• Natural Standard: Authority on Integrative Medicine

• Nursing Reference Center with CINAHL Plus full text

• …

• Published and gray literature

• Hand searching major relevant journals, conferenceproceedings, books and reviews that are not availableonline in full text

• Review references in key articles

• Seek help from domain experts

• Citation management program (EndNote, CiteULike, Mendeley, …)

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Selecting studies

Systematic Review

• Using inclusion and exclusioncriteria defined in protocol.

• Use specific steps defined in a protocol.

Do not forget:

- To remove duplicates if youreview from different sources.

- PRISMA flow diagram is a goodtool for presentation of searchresults.

PRISMA 2009 Flow Diagram

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PRISMA Flow Diagram Example

Systematic Review

• General informationabout PRISMA model:

http://www.prisma-statement.org/

• PRISMAFlow Diagram Generator: http://prisma.thetacollaborative.ca/

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First Pass - Selection of studies by reading thetitles and abstract to check which results actuallymatter to your PICO model

Systematic Review

• Same patients, treatments, diseases, outcome,…?

• Usually required at least 2 reviewers in a team to avoidany errors and biases

• Develop a strategy to resolve disagreements amongreviewers in the team

• Keep a log of all excluded studies and the reasons fortheir exclusion

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Systematic Review

• Recomendation: Each studyshould be assessed by at least two reviewers.

• Check-list or quality scale system to keep track of theassessments.

• Blind the author, institutionand publisher informationof the studies in order to avoid bias.

Second Pass – Obtain and read the full text ofthe included studies and further apraize thequality of those studies using criteria defined in the protocol

QUALIFIED STUDIES FOR THE SYSTEMATIC

REVIEW

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Step 4: Data ExtractionSystematic Review

• Recomendation: Each data extraction should be done by at least tworeviewers.

• Blind the author, institution and publisher information of the studies in orderto avoid bias.

• Design data extraction form and try it on some pilot data:• Study population

• Study duration

• Patient charasteristics (age, BMI, …)

• Outcomes

• Potencial sources of bias (funding source (pharmaceutical company,…), blinding, sampling,…

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Step 5: Analyzing and Presenting DataSystematic Review

• Present the extracted data in summary tables

• If the results are simmilar use meta analysis to combinethe results.

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Example of extracted data in summary table

Systematic Review

The current state of cancer family history collection tools in primary care: a systematic review

Nadeem Qureshi, June C Carroll, Brenda Wilson, Pasqualina Santaguida, Judith Allanson, Melissa Brouwers and Parminder Raina

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Step 6: Interpreting the results

Systematic Review

• Are there some limitations due to unavoidable publication biases?

• What is the strength of evidence of thisresults?

• Are this results applicable and to what?

• Do this results have some economicimpact?

• The ideas for future research.

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Write the report

Systematic Review

• Recomendation: Work with librarian orother specialist trained in performingsystematic review to plan your searchstrtategy and conduct searches!

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Literature

Systematic Review

• http://www.equator-network.org/

• http://library.medicine.yale.edu/

• Julie Glanville, Rachael McCool, What is a systematic review? (http://www.whatisseries.co.uk/what-is-a-systematic-review/)

• Khan, Kunz, Kleijnen, Antes, Five steps to conducting a systematic review, J R Soc Med 2003;96:118–121