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Stony Brook University

Systematic Reviews: The Question

A guide to conducting systematic reviews.

Research Question: PICO

PICO

Patient population (or problem to be addressed):

  • Example: Children aged 3-8 yrs diagnosed with croup

Intervention (Exposure)

  • Example: Use of a specific new drug at a specific dose by a specific mode of administration

Comparison (Control, Placebo, Standard Care)

  • Example: Use of the present drug in standard conditions

Outcomes

  • Examples: Comparative relief of symptoms A, B, C; results of observations D, E, F; or test results G, H,

 

Note that some version of PICO add one or two "T"'s to the end. These may cover such things as:

  • Type of studies wanted (RCTs, CTs, cohort studies, etc.)
  • Type of question (diagnosis, therapy, epidemiology, etc.)
  • Timing of intervention

See, for example: http://www.cebm.net/asking-focused-questions/  and http://www.tripdatabase.com/search/wizard. Many websites provide information on PICO and its adaptations.

Inclusion/Exclusion Criteria

Defining your inclusion and exclusion criteria in advance is just as important in a systematic review as it is in a clinical study.

These are often called “Limits” during search process and are determined by research question.

These criteria determine which ‘subjects’ (studies) will be included in or excluded from the review.

Inclusion/exclusion criteria usually include standard things such as choice of languages, publication dates, publication types, geographical locations, but - more importantly - they may also include your outcomes measures. This is why pre-determining your outcome measures when formatting your question is so useful. If you are looking for studies that report the results of a certain test, any study that doesn't report such results is then excluded from your review.

Also, think about your population carefully, just as you would for a clinical trial. Not just age groups and genders, but also comorbidities and related conditions.