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Research Guides@Tufts

PBL Research Guide

Evidence-Based Medicine

Three-circle Venn diagram. Circles with text indivudual clinical expertise, best external evidence, and patient values & expectations overlap at EBM

• The conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients
• Integrating individual clinical expertise with the best available external clinical evidence from systematic research

DL Sackett, WMC Rosenberg, JAM Gray and WS Richardson, Evidence based medicine: What it is and what it isn't, Br Med J 312 (1996), pp. 71–72.

What's a Foreground Question?

Foreground questions:

  • Ask for specific knowledge to inform clinical decisions for patient care
  • Are formatted using the PICO structure, which is a tool that helps isolate concepts from the foreground question.
  • Have uncertain, context-dependent answers. Inconsistent or inconclusive answers are a feature, not a bug.

For example:

"In smokers with a cough, does a chest x-ray or chest CT have a better positive or negative predictive value for lung cancer?"

Finding Evidence for Foreground Questions

Foreground question resources are at the top of the evidence pyramid: systematic reviews, meta-analyses, RCTs, cohort studies

Resources at the top of the evidence pyramid:

  • Have the most evidence to support their conclusions.
  • Are the best for answering foreground questions.
  • Are less abundant in the literature.
  • Are the most clinically relevant for decision making.

See the sections on point-of-care tools and article databases to find answers to foreground questions.


Breaking a foreground question in the PICO format helps frame the question, and makes it easier to develop search terms to use in databases such as PubMed to find the best evidence.

PICO Acronym

  • P = Patient, population or target problem at hand
    • How would you describe a group of patients similar to your own?
    • What is the condition or disease you are interested in?
  • I = Intervention 
    • What do you want to do to this patient?
    • Treat, diagnose, or observe?
  • C = Comparison
    • What is the main alternative (gold standard) to compare with the intervention?
    • Your clinical question does not always need a direct comparison.
  • O = Outcome
    • What can you hope to improve, accomplish, measure, or affect?
    • What are the relevant outcomes? (e.g. morbidity, death, complications, cost)
If we use the foreground question from the example above, our PICO might look like this:
  • P = Smokers with cough
  • I = Chest x-ray
  • C = Chest CT
  • O = Predicting lung cancer
NOTE! Not all PICOs will have comparisons.

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