Steps in the Process of Evidence-Based Practice
Step 2: Finding the Evidence
Ideally, evidence-based clinical practice guidelines relevant to your clinical question will already exist (see Making the Decision). When that is not the case, however, the clinician needs to seek out scientific evidence to help inform the treatment decision. Two major types of evidence may be useful:
Systematic reviews form the basis for evidence-based clinical practice guidelines. They are formal assessments of the body of scientific evidence related to a clinical question, and describe the extent to which various diagnostic or treatment approaches are supported by the evidence, but stop short of making specific recommendations for clinical practice.
They are useful in helping clinicians make treatment decisions in that, when done properly, they have pulled together and in a systematic way characterized the available evidence on a clinical question.
Where to Find Systematic Reviews
When clinical practice guidelines or systematic reviews are not available, not current, not trustworthy, and/or not relevant, one can turn to individual studies to seek evidence to help make treatment decisions. The first place to find individual studies would be an online bibliographic database. For health care studies, the best place to start would be MEDLINE, the world's largest online bibliographic database of health related studies. MEDLINE cites over 12 million articles from 4,000 peer-reviewed journals.
Unfortunately, publication in a peer-reviewed journal is not a guarantee of scientific quality. It is also important to keep in mind that studies published in English langauge, and particularly American journals, are less likely to include studies with negative findings than are European and other non-English journals. In order to get a comprehensive view of the evidence, both positive and negative, searching a European database such as CINAHL®, the Cumulative Index to Nursing and Allied Health Literature, is valuable. Although CINAHL is more likely than MEDLINE to contain studies with negative findings, it is still more likely to publish a study with a positive than a negative finding. To find studies with negative findings, and indeed some with positive findings, one can look to the "gray" literature. The gray literature is the term given to the body of research that is not published in peer-reviewed literature. This can take the form of technical reports, conference proceedings, testimony and other unpublished evidence. Finding the gray literature is a difficult task and is typically done through conversations with content experts, relevant professional groups/organizations, and internet search engines.