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Clinical Questions: Get going

Clinical question searching

Answering a clinical question according to the Evidence-Based Medicine (EBM) method involves a systematic literature search to locate the best scientific evidence.

On the basis of the evidence found, an answer to the question is formulated.

This answer, together with clinician's expertise and patient's preferences/values, can be used in taking clinical decisions.


For clinical search questions, different research databases may be used, such as:



(in yellow: the steps that are supported by University Library Utrecht)

When searching, mind the following

  • Develop a good search question in which all aspects of your topic are addressed. Use all these aspects in your search.
  • Use (subject) specific search terms, synomyms and descriptors for every aspect of your search question.
  • If necessary, use methodological search filters (Clinical Queries in PubMed) to limit your search result by type of question (therapy, diagnosis, prognosis, etiology).
  • Use Citation searching (following up citations and references) to track down relevant articles.

Levels of evidence

Evidence pyramid - (c) Copyright 2006 - 2011. Trustees of Dartmouth College and Yale University. All Rights Reserved. Produced by Jan Glover, Dave Izzo, Karen Odato, and Lei Wang

In principle, a good systematic review (for instance in Cochrane Library) has the highest level of evidence.

Critically Appraised Topics (CATs) are often less extensive in scope than systematic reviews; when carefully carried out, they provide good quality of evidence.

The quality of evidence of individual studies (for instance in PubMed) varies with the type of study: randomized controlled trials (RCTs) have a higher quality of evidence than cohort studies, but are often only available for therapeutic questions.

Please note: Guidelines are often a combination of evidence-based recommendations and expert opinion.


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This LibGuide has been developed in close collaboration with UMC Utrecht.

What's in a name?

Different terms are used to denote answering a clinical question using the EBM-method:

  • CAT: Critically Appraised Topic. The CAT is a compulsory part of the training program of medical specialists (AIOS)

  • PICO: an abbreviation of the different parts of a clinical question ((Patient-Intervention-Comparison-Outcome), but is sometimes  used as a synonym for CAT.

  • Question of the week: the interpretation given to the CAT within the department Internal Medicine in UMC Utrecht.

Jargon in plain language

  • systematic review
    a  review of the literature, conducted according to explicit and reproducible methods, for the selection and validation of individual studies
  • meta-analysis:
    a systematic review containing not just a descripitve, but also a quantitative comparison of the results of individual studies
  • randomized controlled trial
    experimental study in which test subjects are randomly assigned to either the treatment group or control group
  • cohort study
    observational study in which subjects with or without certain risk factors are followed for a length of time, to ascertain how a certain disease is developed
  • case-control study (patient-control study)
    observational study in which a group of patients is compared to a healthy control group, and the existence of risk factors in the past is taken into account.