What is Evidence-based Practice?

There are many definitions of evidence-based practice. One of the most widely cited is by Sackett (1996) and refers specifically to evidence-based medicine, but applies similarly to health care in general:


“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.”


The concept has been widely embraced in a wide range of allied health areas, and the term “evidence-based practice” is used, as in this definition by Dawes et al (2005):


"Evidence-Based Practice (EBP) requires that decisions about health care are based on the best available, current, valid and relevant evidence. These decisions should be made by those receiving care, informed by the tacit and explicit knowledge of those providing care, within the context of available resources.”


More recently, Satterfield et al (2009) pointed out that EBP is limited or facilitated by the environment in which the clinical decision is made (the clinical organizational structure), so that EBP is a combination of:


1. The best external research evidence

2. The practitioner’s expertise and experience

3. The patient’s characteristics, presentation and preferences

>>> all set within the organisational and environmental context of the practice environment.

What does this actually mean in practice though?


Essentially, evidence-based practice can be thought of as a process in which clinical decisions are made in light of the best research evidence, existing practitioner expertise and knowledge and the patient’s preferences within the context of the clinic environment.

The following diagram helps to visualise the relationship of each of these with the final product of clinical decision-making as the culmination of using all of the elements together.:

From Satterfield et al (2009) Toward a Transdisciplinary Model of Evidence-based Practice.
Millbank Quarterly 87(2): 368-390.
(With permission)

Putting this all together is a skill that needs to be learned, but it is essentially what experienced clinicians of all professions do all the time - EBP just makes this clear and easier to teach practice at an undergraduate level. It also clarifies our approach.

In conclusion, when practitioners consider all of the factors shown in the above diagram as part of clinical decision-making, the process they have followed is evidence-based practice. This EBP process can be defined into 5 STEPS of EBP as is detailed in the EBP In Action section.


The patient or population characteristics and preferences

All through the EBP process we take into account the characteristics of the patient in front of us. For example, we search for evidence relevant to this type of patient and population. At the 'Apply' stage, a clinical decision is made on the basis of that evidence, we take the patient's preferences and values into account. We discuss the evidence with the patient and so that the clinical decision takes into account not only the evidence and our expertise but also the patient's perspective. 

Practice environment

As indicated above, clinical decisions are made in the context of the practice environment, which may limit or facilitate the EBP process. For example, the practice may not provide Internet access, in which case the practitioner may not have immediate access to research evidence. 

However, the practitioner would need to not only access but also appraise the evidence before applying it as part of clinical decision making. This in itself is a limitation to EBP in optometry, since proper appraisal of research reports is time consuming, and not feasible in a chair-side situation. In medicine and some allied health areas, systems are in place to provide pre-appraised reports of the available research evidence, but unfortunately no such systems exist currently for optometry or any eye care profession.

Another practice environment factor is the ethos of the practice, which may support the use of best available research evidence, or not. Thus, practitioners may be part of a mind-set in which EBP is the norm, and is encouraged, or in which the EBP process is unusual and not generally embraced. This and other environmental factors could influence the extent to which each practitioner is likely to follow EBP process when making clinical decisions.


Best evidence

This term refers to the highest quality evidence from research that is available to the practitioner, and “highest quality” refers to grading of published research based on the extent to which the evidence provided by this research can be considered reliable. One such grading system comes from the Australia based National Health and Medical Research Council (NHMRC). Note though that low level 'evidence' may be found in non-research sources. For example, the Centre for Evidence-based Medicine (CEBM) lists expert opinion as the lowest of five levels of evidence, and points out that if the best available evidence is very low level/low quality, our advice to patients should include information on the degree of reliability or otherwise of the evidence.

According to the NHMRC scale, the CEBM table and other evidence heirarchies of this kind, case reports are toward the low end of the scale. They are of limited reliability because they are observations of individual cases. If the case involves an intervention, the reported results may reflect a placebo effect since there was no comparison with a placebo intervention. In case studies not involving intervention, the patient’s response may reflect a Hawthorne effect if the patient knew they were being observed. At the other end of the scale we have randomized controlled studies and systematic reviews of such studies.

These provide more reliable evidence because a larger sample of the population was included (individual cases may not be typical of the wider population), the sample was randomly allocated to groups treated differently (e.g. with real, placebo or no interventions) and the study was controlled (with a placebo comparison). In addition, a high quality study would be expected to include masking of the patients and the researchers, so that neither were aware in which cases the placebo or the real intervention applied. This minimizes the chance of either being biased toward a certain type of outcome, and illustrates the fact that we cannot assume that a randomized controlled study provides solid evidence. The details of the study methodology must be understood in order to assess internal validity, that is, to determine whether the results may reflect factors such as bias or other flawed methodology.

For any clinical question, if research evidence at the high end of the scale (e.g. a systematic review of randomized controlled trials) is in publication, but the practitioner does not access and use it as part of clinical decision making, the process followed cannot be said to be ‘evidence-based’. However, if high end research evidence is not in publication, the practitioner has no option but to use lower quality evidence, such as studies that were not properly randomized, or perhaps even no research evidence. In such circumstances, the process does fit the definition of evidence-based practice, if the practitioner is using the best available evidence (the word “available” is often used in definitions of EBP ; Sackett, 1996; Cochrane, 2012) together with clinical experience/expertise and the patient’s preferences in the context of the practice environment.

So, “best available research evidence” is the highest quality (most reliable) research that is in publication, and therefore available to the practitioner for appraisal and application as the basis of clinical decision making. Note that details of the research may not be easily available, because they are often not provided via ‘open access’ (freely available to all via the Internet) so they can be accessed only with journal subscription or as part of professional body membership or University enrolment. The evidence is thought of as being available to the practitioner if full details are published somewhere, even if access incurs cost.

The evidence that the practitioner finds must be appraised before being applied - appraisal is STEP 3 of EBP.


Clinical expertise

Another term in the definitions of EBP is “clinical expertise” or “clinical experience”. To refer again to Sackett (1996) “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.” So, this aspect of EBP is the experience and knowledge the practitioner has gathered through hands-on clinical practice.





EBP process: 
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