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Systematic Reviews in the Health Sciences

What type of question?

Once you have formulated a focused clinical question using PICO, it is also useful to decide what type of question it is. 


How can we find out whether or not a person has a
specific condition or illness?


How can we prevent or treat a specific condition,
llness or problem?


What happens to a person with a specific
condition or illness?


Why does a person get a specific condition
or illness?


How does it feel to have a specific condition,
illness or problem?


What type of study?


Type of question

Type  of study


Controlled trials, Cross-sectional studies


Randomized controlled trials


Cohort studies


Cohort studies, Case control studies


Qualitative studies

Cost Benefit

Economic analysis

Why do I need a protocol?

A major cause of bias in a systematic review is answering a different question to that being originally asked. This is why it is important to develop a review plan or protocol.

The benefits of having a protocol before the beginning of a review:

  • relate to the validity and merit of a research process that reduces risk of bias
  • promotes a systematic rather than ad hoc approach to the review process
  • facilitates communication with others and promotes consistency between review team members
  • support the reliability and usefulness of reviews to health professionals

What are the steps for a protocol?

  1. Check existing reviews/protocols - a decision needs to be made whether to abort the review or amend the question.
  2. Formulate a specific question -  PICO (for a quantitative review) - PICo (for a qualitative review)
  3. Inclusion criteria – puts the question into operation (population, intervention or comparison, outcome, study design, language, publication)
  4. Exclusion criteria for not including certain studies e.g. specific populations, language, setting
  5. Eligibility criteria for including studies– qualitative and quantitative (study design, language, date of publication, duplicate data)
  6. Search strategy - explicit and reproducible (can include grey literature)
  7. Critical appraisal - assess risk of bias in individual studies
  8. Synthesis of results - interpret/analyse results, determining the applicability of results
  9. Report - comprehensive report on all steps of the systematic review and presents results