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Cochrane Library (English): 1. Research Question + PICO

Formulating your research question

Before searching formulate a good and clear clinical question. This is often underestimated. It is tempting to start searching immediately and type some terms in the search bar. Unfortunately the result is mostly unsatisfactory: too many irrelevant hits. The question should be formulated in a way that allows the finding of a meaningful answer.

Splitting the research question

Do you have a good research question?
Split it into sub-elements.
You can do this by using:

  1. PICO method
  2. Building block model


PICO method

By reframing your research question into PICO elements you are forced to think ahead of the outcome you want.

P = patient / population / problem
I = intervention / (diagnostic) instrument
C = comparison
O =


It is not necessary to use all the PICO elements. Sometimes only P and I will do.

Firstly, search each PICO element. Search for matching search terms and think of as many synonyms as possible. Then combine the PICO elements. Use the right search terms and the combination will give you an answer to your research question.



I - Only one intervention per PICO is allowed. More interventions = more PICOs.
C - Not very common. A lot of researches are already comparative studies. Only use C if you want to compare two different therapies.
O - Is your outcome the effect of an intervention? Then do not use O, choose RCT as publication type.
M -

It may be relevant to add method (RCT, systematic review) or domain (therapy, diagnosis, prognosis) to your PICO. See also tab Step 6 - Filters & Clinical Queries in the LibGuide on PubMed.

Building Block method

It is not always possible to turn your research question into a PICO. Then use the building block method instead. The principle is the same as PICO. Extract the core elements of your question (building blocks). Search matching search terms per element and add synonyms. In the end you combine the elements. | Disclaimer | Over Zuyd Bibliotheek