Once you have formulated your question and understand what you are looking for, you may find what you need in a filtered resource (See Evidence Pyramid and Resources tab). In these, clinical experts have done the work for you—searching the literature, evaluating studies, providing summaries and analyses and making recommendations for practice. These still need to be evaluated by you for appropriateness for your specific situation and patient, but they can save time and ensure completeness.
Sometimes, though, you will be unable to find an answer in a filtered resource and will have to do your own search of the literature for primary research studies. Use the search techniques you’ve learned to search databases such as PubMed or CINAHL for such literature.
PICO can help you identify appropriate search terms and other search parameters (such as age, sex, language, year of publication, etc.). (See the Worksheet on the PICO tab.) And there are techniques that can be used in article databases such as PubMed Web of Science that will help you focus for evidence-based literature.
On the main search screen (link is below the main search box), in the Limit Your Results area, select Cochrane Reviews; this will rule out Protocols—not yet completed reviews.
Once you have done your basic search, use the Limits to choose Publication Types that are appropriate to evidence-based practice:
PubMed also has a special feature PubMed Clinical Queries, intended for clinicians, which has built-in search "filters" for detecting clinically sound studies. Four study categories--therapy, diagnosis, etiology, prognosis--are provided, and you can choose the emphasis to be either specificity (i.e., mostly relevant articles but maybe missing a few) or sensitivity (i.e., most relevant articles but maybe some less relevant ones). There is also a Systematic Reviews Subset Strategy which can be appended to any search.
TRIP uses a color-coded hierarchy of evidence, based on various categories such as Evidence-Based Synopses, Guidelines, etc. Use the “Filter by” function on the left-side of the screen to limit your results to that category. Click on "Search Wizard" under Labs at the bottom of the homepage for a PICO template for searching.
Depending of the clinical/research question, a certain study type can often provide the best answer. Keep in mind that RCTs are not always available or even possible for every therapy/intervention, and that certain questions are appropriately answered by studies that are lower on the EBM pyramid. Systematic Reviews provide higher-level evidence that single RCTs and other types of studies, so you should select SRs when they are available.
|Question Category||Study Type|
|Diagnosis||prospective, blind comparison to a gold standard|
|Prognosis||cohort>case control>case series|
These are a few of the study types associated with evidence-based practice taken from the Glossary of EBM Terms from the Centre for Evidence-Based Medicine Toronto:
Meta-analysis: A systematic review that uses quantitative methods to synthesize and summarize results of studies.
Systematic Review: A summary of the medical literature that uses explicit methods to perform a comprehensive literature search and critical appraisal of individual studies and that uses
appropriate statistical techniques to combine these valid studies.
Randomized Controlled Trial: A study in which participants are randomly allocated into an experimental group or control group and followed over time for the variables/outcomes of interest.
Cohort Studies: Involves identification of two groups (cohorts) of patients, one which received the exposure and one which did not, and following these cohorts forward for the outcome of interest. These studies can be Prospective or Retrospective.
Case Controlled Studies: A study which involves identifying patients who have the outcome of interest (cases) and patients without the same outcome (controls), and looking back to see if they had the exposure of interest.
Case Series: A report on a series of patients with an outcome of interest. No control group is involved.