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Universiteitsbibliotheek – LibGuides

Clinical Questions: Find out more

Critical appraisal

The articles retrieved that best seem to answer your question should be judged by:

  • relevance: are the results useful for the patient / the case that lies at the base of your clinical question?
  • validity: has the study been methodologically well performed? What is the level of evidence of the type of study?

For carrying out critical appraisal several checklists are available:

A good search question: Domain, Determinant, Outcome (DDO)



Formulate a good search question in which the different aspects (domain, determinant and outcome) of your research topic are identified. Which aspects are relevant, depends among other things on the type of question (diagnosis, prognosis, therapy).

Generating search terms

Choose the most common (subject) specific search terms and synonyms for every aspect of your search question. Remember to use alternative spellings, singular and plural forms when necessary. In addition, use the standard subject keywords of the data bases you work with.

You will find general information on how to choose the right search terms in the LibGuide Generating search terms.UBU LibGuide Zoektermen bedenken

Opstellen van een zoekstrategie Building a search strategy


For every aspect of your search question, search using all search terms, synomyms and subject keywords you have collected. Combine these with OR. Then combine the search actions on the different aspects (with the AND operator). That way, you will be left with just those articles that address all aspects of your search question.

Information on how to carry out a search strategy in different search engines (notably PubMed and the Cochrane Library) you will find in the Train yourself tab of this LibGuide.

For more information on building a search strategy in general you are referred to the LibGuide Zoekstrategie (in Dutch).


Instead of using the DDO model:

- Domain
- Determinant
- Outcome

a clinical question is also often formulated using the PICO model:

- Patient
- Intervention
- Comparison
- Outcome

Both models can be used.