Monday, March 30, 2009

Finding Evidence

The Users’ Guide to the Medical Literature states that “assessment of knowledge gaps, question formation, gathering and synthesis of evidence, and application of that evidence to the care of patients are among the foundations of informed care.” (1) At Palmer we are contextualizing evidence-based practice in terms of patient care; we have used the PICO model to derive meaningful clinical questions that can be effectively searched in order to be answered. Thus, in terms of process, we look initially at a clinical case scenario; a patient presents some sort of challenge to a physician, who then must develop a clinical question to search for evidence, assess the evidence and then apply the evidence and monitor results.

Key in this is finding evidence. We locate evidence through the judicious use of information sources. The Users’ Guides categorizes information sources into four categories:

Systems: These are textbook-like resources that provide regularly updated clinical evidence. This may or may not be integrated with other forms of health care information, and which typically will also provide guidelines for patient care. An example of a system would be UpToDate (

Synopses: These are sources which provide preappraised resources of recent journal articles and publications. One classic resource for synoptic evidence is the ACP Journal Club (

Summaries: This is where you would locate systematic reviews of health care interventions. The major source that we are familiar with is the Cochrane Collaboration ( It is also possible to locate systematic reviews using the clinical queries link on PubMed. These reviews examine individual studies which meet inclusion criteria and then provide recommendations based on analysis of effect sizes and other data.

Studies: Of course, we should not forget that another great resource are individual studies themselves, as published in clinical literature. The challenge for us in using individual studies is we need to be able to evaluate the study before use, and this requires a certain skill set to do so most effectively.

In order for you to do the most effective search, you need to know how best to choose the appropriate information resource. Once again, the Users’ Guides offer suggestions. They find four important criteria for choosing a resource.

Soundness of evidence-based approach: The resource should provide access to a proper sample of high-quality evidence for your question It will address validity and outcomes of interest.

Comprehensiveness and specificity: Different resources have different goals and strengths. For example, Cochrane is useful when looking at management, but is not useful if your interest is in diagnostic accuracy. You need to ensure that the tool you choose is best able to answer the question you are interested in.

Ease of use: Think about how hard it is to construct an effective search in PubMed. How you need to understand syntax, logic and organization in order to structure a search query that helps cut out dross and unnecessary information. Then, consider how easy it is to go to Cochrane and find topical information related to your needs. Ease of use can be a compelling reason to use one website over another.

Availability: Not all sources are free, and some are quite expensive. Within the confines of an academic institution, we might have access to a great deal of information, bur for our students they will lose that access upon their graduation. We should familiarize ourselves with the best free sources of information, of which there are many.

This is then an overview for a look at good resources. That will be covered in the next blog post.

1. Guyatt G, Rennie D, Meade MO, Cook DJ. Users’ guides to the medical literature. New York, NY; McGraw Hill, 2008:30

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