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Evidence-Based Practice for the health disciplines

Evidence-Based Practice

Evidence-based practice (EBP) was developed from the concept of evidence-based medicine and has been extended and applied to many different disciplines, particularly in the health sciences.

"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 centered 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."

Sackett, D., Rosenberg, W., Muir Gray, J., Haynes, R. Richardson, W.  (1996). Evidence based medicine: what it is and what it isn't.  British Medical Journal, 312, 71-72.

To obtain evidence from systematic research, scholars must often use the library resources. Therefore, knowing where to look, how to search, how to evaluate, what to choose, how to store, and how to manage the information from the library or other information source is very important.

Levels of Evidence

Levels of evidence may vary by author, publication, or source. Check with your instructor to see what definitions are being used for levels of evidence in your class. However, regardless of whether your definition uses 3, 4, or 5 levels of evidence, the value of the evidence provided by the different types of publications remains unchanged.

Rating System for Levels of Evidence
(Rated best to least reliable)

Level I     Evidence from a systematic review or meta-analysis of all relevant randomized controlled trials or Evidence based clinical practice guidelines based on systematic reviews of RCT’s
Level II    Evidence obtained from at least one properly designed randomized control trial
Level II    Evidence obtained from well-designed controlled trials without randomization
Level IV   Evidence obtained from well designed case control and cohort studies
Level V    Evidence from systematic reviews of descriptive and qualitative studies (meta-synthesis)
Level VI   Evidence from a single descriptive or qualitative study
Level VII  Evidence from opinion of authorities and/or reports of expert committees

              (Modified from: Melnyk & Fineout-Overholt, 2010; Guyatt & Rennie, 2002 and Harris et al., 2001)


Centre for Evidence-Based Medicine  

Level 1     Systematic reviews or meta-analyses
Level 2     Randomized controlled trials
Level 3     a. Cohort studies (with control group)
                  b. Case-controlled 
                  c. Observational studies (without control group)
Level 4     Expert opinion, physiology bench research, or consensus

Dr Joseph F Smith Medical Library, Aspirus

Adopted from EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.
Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.  

About Levels of Evidence

Levels of evidence represent an attempt to categorize different publication types into a hierarchy of "better" information. "Better" information is less likely to be tainted by bias, errors, coincidence, etc.

Obviously, expert opinion provides better information than inexpert opinion. Research studies provide more accurate information than opinion, expert or inexpert. Studies with control groups are more accurate than studies which do not compare to a control group. Randomized controlled studies provide more accurate information than studies where research subjects are not randomly assigned to control and trial groups. Double-blind, randomized controlled studies are even less likely to be affected by researcher or research subject bias than studies which are not double-blind. And systematic reviews and meta-analyses, in which multiple similar studies are compared to each other, are more reliable as an indication of whether an outcome is correlated to a particular intervention or variable than a single research study.


Use PICO to develop a clear idea what information you are seeking. PICO was developed by faculty at McMaster University.

P   Population/Patient/Problem

What group will be acted upon? What group will experience the change in order to become better?

I    Intervention

What change is being done to the population?

C   Comparison

Changed from what? To what is the change being compared?

O   Outcome 

What is the desired effect or result of the change on the population?

T     Time

What is the time frame to see the effect? Short term or long term effects? (not always included in a PICO)

PICO is a tool to help you organize your thoughts and formulate a search strategy. Use the components to break your research question down into parts and enter them in an appropriate manner into a search of your database.

In summary you are trying to make a change (the Intervention) from some other old way (the Comparison) for someone (the Population) to make things better in some way (the Outcome).

Be flexible! Different databases may require different methods to limit to specific population groups. And realize that you may be interested in an intervention's effects on pregnant women, but little research may have been done on pregnant women due to ethical and safety reasons. (If so, look for the next best thing--research on the effects on women or whatever populations have been studied. Then extrapolate the known effects to propose what is likely to happen to pregnant women, the unknown. Remember to acknowledge the extrapolation.) 


POEM stands for Patient-Oriented Evidence that Matters. It is health information that is useful, relevant, and easily obtainable. Only meta-analyses and original research are used to create POEMs.

POEMs must:

  • Address a clinical question faced by health care professionals
  • Measure outcomes that are important to clinicians and patients, such as symptoms, morbidity, quality of life and mortality
  • Have the potential to change practice

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Will Rogers

"It isn’t what we don’t know that gives us trouble, it’s what we know that ain’t so."

Will Rogers