"Evidence based medicine is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research. By individual clinical expertise we mean the proficiency and judgment that individual clinicians acquire through clinical experience and clinical practice. Increased expertise is reflected in many ways, but especially in more effective and efficient diagnosis and in the more thoughtful identification and compassionate use of individual patients’ predicaments, rights, and preferences in making clinical decisions about their care. By best available external clinical evidence we mean clinically relevant research, often from the basic sciences of medicine, but especially from patient centred clinical research into the accuracy and precision of diagnostic tests (including the clinical examination), the power of prognostic markers, and the efficacy and safety of therapeutic, rehabilitative, and preventive regimens." (p. 71)
from Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn’t. BMJ. 1996;312(7023):71-72.

ASK - Formulate a specific clinical question, using the PICO or PICOTT formula.
  • Patient
  • Intervention
  • Control
  • Outcome
  • Type of Question
  • Type of Study

How-To Examples on formulating a specific clinical question using the PICO or PICOTT formula: EBM Librarian's Teaching Tools > Scenarios, with PICO and MeSH

Search Tertiary Literature

Search Primary Literature
Is your clinical question about therapy, diagnosis, prognosis, or etiology/harm? Consult Duke University Medical Center Library & Archives' Hierarchy of Evidence chart for the type of study needed to answer your question.
For pharmacists, the clinical question will likely be about therapy/pharmacotherapeutic intervention(s). To compare therapeutic interventions, look for randomized controlled trials, meta-analyses, or systematic reviews.

APPRAISE - Critically Appraise Literature

Critical Appraisal Worksheets, with completed examples:

Appraising Randomized Controlled Trials (RCTs)

Evaluation of RCT Results for Validity criteria published in
  • Guyatt GH, Sackett DL, Cook DJ. Users’ guides to the medical literature. II. How to use an article about therapy or prevention. A. Are the results of the study valid? Evidence-Based Medicine Working Group. JAMA. 1993;270(21):2598–2601. and
  • Guyatt G, Rennie D, Meade MO, Cook DJ. Users’ guides to the medical literature: a manual for evidence-based clinical practice. 2nd ed. New York: McGraw Hill Medical; 2008.
In the trial:
1. Were patients randomly assigned, that is, had an equal chance of being assigned to either treatment group? Randomization limits selection bias.
Video definition of randomization. Video by the South Carolina Clinical and Translational Institute.
2. Were all patients accounted for in follow-up and the study’s results? “Every patient who entered the trial should be accounted for at its conclusion.”
i. “The greater the number of subjects who are lost, the more the trial may be subject to bias because patients who are lost often have different prognoses from those who are retained, and may disappear because they suffer adverse outcomes (even death) or because they are doing well….”
ii. Attribute all patients to the group to which they were randomized.
Video definition of intention-to-treat analysis. Video by Dr. Allen F. Shaughnessy, PharmD, MMedEd, Tufts University School of Medicine
3. Was the allocation of patients to groups concealed to the investigators assigning patients?
Video definition of concealed allocation. Video by Dr. Allen F. Shaughnessy, PharmD, MMedEd, Tufts University School of Medicine
4. Were the study’s investigators, practitioners, and/or participants blinded to which of the two therapeutic interventions being compared was being given to a patient? Blinding, which may not always be possible, limits assessment and reporting bias.
5. Were the study’s groups similar in their baseline characteristics?
“[R]eaders would like to be informed that the treatment and control groups were similar for all the factors that determine the clinical outcomes of interest save one: whether they received the experimental therapy. Investigators provide this reassurance when they display the entry or baseline prognostic features of the treatment and control patients.” II.A. pg.2600
6. Did participants in both groups receive equal treatment?
“[D]ifferences in care other than that under study can weaken or distort the results.”

Are the results of a study important?
Complete a 2 x 2 or contingency table and calculate the number needed to treat (NNT):

Appraising Systematic Reviews or Meta-Analyses

APPLY - Apply findings to your patient

History of Evidence Based Medicine
Works Consulted

Return to the ACP library web site.

Please contact the ACP library with any questions.
e-mail: library@acp.edu
phone: (276) 498-5239

Rev. 01/17