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Searching for the right evidence: how to answer your clinical questions using the 6S hierarchy
  1. Donna Windish
  1. Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, USA
  1. Correspondence to Donna Windish
    Department of Internal Medicine, Yale Primary Care Residency Program, Yale University School of Medicine, 64 Robbins Street, Waterbury, New Haven, CT 06708, USA; donna.windish{at}

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Asking and answering clinical questions during daily practice can be challenging and time consuming. Knowing the resources available to answer a specific clinical question can lead to a more efficient and effective search strategy and thus, to a more applicable answer based on the levels of evidence available. This primer reviews how to search for the right evidence using a specified hierarchy and provides examples of pre-appraised resources with corresponding websites to help with your search.

View this table:
Table 1

Clinical questions and available resources associated with the 6S model of evidence

Studies (base of the pyramid)

Clinical question

I want to find the latest treatment for my patient's illness and want to use an evidence-based approach (ask, acquire, appraise and apply). Where should I look for this information?


In this case, searching the primary literature for single articles would be best.

Sample resources

PubMed; Clinical Queries; international literature searches through EMBASE; topics of nursing, biomedicine, health sciences librarianship, alternative/complementary medicine and consumer health through CINAHL; PsycINFO (see table 1 for corresponding websites of all sample resources in this article).


The most updated studies are readily available both online and in print. Many of these resources provide alerts when new articles in a topic of interest are published.


When using original studies, you need to understand how …

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  • Competing interests None.