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Public Health: Systematic Literature Reviews

What is a Systematic Literature Review?

A systematic review is a review of scientific studies on a specific topic. It utilizes a formal process to:

  • identify all relevant studies
  • assess their quality
  • summarize the evidence 

*From The Community Guide Methodology

PICO Framework

The PICO framework is used to frame and answer clinical or health-related questions. 


PICO component Building Question Example
P - PATIENT/POPULATION/PROBLEM How would you describe this group of patients? "In patients with heart failurefrom dilated cardiomyopathy who are in sinus rhythm..."
I - INTERVENTION Which main intervention is of interest? "...would adding anticoagulation with warfarin to standard heart failure therapy..."
C - COMPARISON  What is the main alternative to be compared with the intervention? "...when compared with standard therapy alone..."
O - OUTCOME What do you hope the intervention will accomplish? "...lead to lower mortality or morbidity from thromboembolism? Is this enough to be worth the increased risk of bleeding?"

*From PubMed Health Standards for Initiating a Systematic Review


PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

PRISMA is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses.

PRISMA checklist and flow diagram

Systematic vs. Traditional Literature Reviews


Literature Reviews:

  Systematic Traditional


2 or more authors are involved in good quality systematic reviews, may comprise experts in the different stages of the review

1 or more authors usually experts in the topic of interest

Study Protocol:

Written study protocol which includes details of the methods to be used

No study protocol

Research Question:

Specific question which may have all or some of PICO (Population, Intervention, Comparison, and Outcome) components. Hypothesis is stated

Broad to specific question, hypothesis not stated

Search Strategy:

Detailed and comprehensive search strategy is developed

No detailed search strategy; search is usually conducted using keywords

Sources of Literature:

List of databases, websites and other sources of included studies are listed. Both published and unpublished literature are considered

Not usually stated and non-exhaustive, use well-known articles. Prone to selection bias

Selection Criteria:

Specific inclusion and exclusion criteria

No specific selection criteria, usually subjective. Prone to selection bias

Critical Appraisal:

Rigorous appraisal of study quality

Variable evaluation of study quality or method


Narrative, quantitative or qualitative synthesis

Often qualitative synthesis of evidence


Conclusions drawn are evidence-based

Sometimes evidence-based, but can be influenced by author's personal belief


Accurate documentation of method means results can be reproduced

Findings cannot be reproduced independently as conclusions may be subjective


Systematic reviews can be periodically updated to include new evidence

Cannot be continuously updated

*From Weyinmi Demeyin's blog post. 

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