What Does “Best Evidence” Mean in Evidence-Based Practice?

Last week I introduced the topic of evidence-based practice or EBP.  The evolution of EBP into the healthcare mindset, as opposed to traditional or authority-based practice, has been gradual, but is now part of the healthcare vernacular and, indeed, accepted as the way that modern healthcare clinicians should be practicing their discipline (e.g., medicine, nursing, respiratory care, pharmacy, physical therapy, nutrition, etc.). This post will hone in on the topic of Best Evidence. 

Pie chart of three EBP components with Best Evidence circled

(c) CJT Consulting & Education

The three main components of EBP are best evidence, clinical expertise, and patient preferences and values.  Today I’ll start explaining each of these components and add in the Nursing perspective for how to operationalize each of these pieces so that decision-making is truly informed by evidence from science, clinical experience, and the patient’s/community-of-interest’s viewpoint.

If you missed my free handout on EBP, you can download it by clicking on the link

What Evidence is Acceptable for EBP? 

EBP is all about evidence, but what evidence is acceptable to use for clinical decision-making? Scientific research studies are the foundation or the heart of EBP — the fact that science was not routinely used for practice decisions is how EBP got its start!  Dr. Archie Cochrane, a Scottish epidemiologist and physician, is credited with expressing the fact that many commonly used and accepted medical interventions had no reliable evidence base to support their use in medical practice (Stavrou, Challoumas, & Dimitrakakis, 2014). 

Randomized Clinical Trials and Systematic Reviews

Cochrane promoted the use of randomized controlled trials (RCTs) as trustworthy scientific evidence for choosing medical interventions, not tradition and clinical experience alone. Cochrane also voiced the need for systematic reviews of the current science.

A systematic review is a systematic method to gather the current data from research studies about a medical topic into one definitive source of information for clinician decision-making.  A meta-analysis is a systematic review of quantitative studies from which a summary statistic can be derived.  He also introduced the concept of cost-effectiveness in medicine (Stavrou et al.).  

Cochrane’s innovative thinking led to the founding of evidence-based medicine, which evolved into evidence-based practice or evidence-based healthcare. The Cochrane Collaboration is a non-profit organization “dedicated to making up-to-date, accurate information about the effects of healthcare readily available worldwide. It produces and disseminates systematic reviews of healthcare interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions” (http://us.cochrane.org/cochrane-collaboration) and is named after Dr. Cochrane. 

Scientific research is the preferred main source of evidence to answer clinical questions – it’s where the clinician wants to search for data first — especially about treatment options. Why? Because if you remember from your research course, RCTs are the strongest studies methodologically — they control the variables and methods so that decreasing random and systematic biases are limited– if they are well-conducted. Decreased bias works to help the researchers confidently make the case that the intervention being tested was responsible for the outcome – and not something else. Therefore, RCTs help us determine cause and effect.  Descriptive/observational studies cannot claim the same. 

For example, when deciding on whether to use Intervention A for your patient — you want to use the intervention that has been shown to work in your particular patient population, right?  So, everything else being equal, if you have a choice of studies to back up your decision you would choose the RCT over an observational or descriptive study.  And if you can find a Cochrane meta-analysis of Intervention A, that’s even better because it would analyze all of the quality RCTs on Intervention A and come up with an overall summary statistic (usually an odds ratio) that will further help you make a decision with your patient.  Make sense?

Nursing and Best Evidence: RCTs are not the predominant form of study method in nursing research – and that’s why some nurses feel that EBP should not be a framework for nursing practice (more on EBP misconceptions later). Of course, RCTs are not appropriate, nor would they be ethical to conduct, for all clinical questions; especially some of the questions of interest to nursing.  Yes, look for high-quality RCTs when making decisions about treatments or interventions, but basing your practice on best evidence does not preclude your acceptance of research findings from of other types of research design! Well-done research studies (e.g., quasi-experimental studies, descriptive or observational studies, metasynthesis, or qualitative studies) are important to building our scientific base for nursing practice. Just always search for the strongest evidence to back up your interventions. 

Let me give you the key to EBP: Regardless of whether you are a nurse, physician, or other healthcare professional you HAVE to APPRAISE the literature to know whether you can trust the results!


  • The rigor of the methods is paramount to your belief in the validity of the research results.  It’s all about how well the researcher conducted the study! 
  • So that, if the research methods are suspect — that is, you have serious misgivings about the quality and rigor of the research methodology (note: novices to critical appraisal will find every study seriously flawed!) — you cannot believe the results! Period. End of story. Stop reading the study and find a better one.

Now no worries!  Not sure how to judge a study’s quality? Ask your Clinical Nurse Specialist (CNS) to appraise the study – or better yet, do the appraisal together or bring the study to the unit journal club so everyone can assess the quality.  No CNS? You can also find a credible database of pre-appraised literature as your go-to source — they do the work of critical appraisal for you! More on this topic, the hierarchy of evidence (levels of evidence), and the critical appraisal of research studies in future posts.

Non-Research Sources of Evidence

While research is the heart of EBP, EBP incorporates additional forms of evidence besides research findings, especially when original research is not available,  accessible, or is considered methodologically weak.  In those cases, we need to use other forms of evidence, which include nonresearch sources, such as:

  • Clinical Experiences of the Clinician/Practitioner
  • Knowledge Of Pathophysiology
  • Quality Assurance/Quality Improvement/Risk Data
  • Professional Standards Of Care/Guidelines
  • Cost Data
  • Benchmarking Data
  • Chart Audit Data
  • Infection Control Data
  • Expert Consensus
  • Patient Preferences and Values

So you can see that EBP is more encompassing than just using research study findings (research-based practice) because you are using all available evidence to inform your decisions.  Keep in mind that, depending on your clinical question, certain types of data may carry more weight or be more informative than others.  You want the Best Evidence!

Most likely, you will probably use more than one source of evidence when deciding on a course of action with the patient and the health care team.  But the fact remains that, the more valid data you can gather that point to a specific course of action, the more confident you’ll be of your decision for that action.

Don’t forget to download my free handout on EBP!

Bottom line: You should always look for the highest level of evidence (i.e., best evidence) possible, but also realize that a well-done study from lower on the hierarchy of studies list will provide stronger, more trustworthy results than a poorly done study from higher on the list. 

What questions do you have on this topic of Best Evidence? Let me know in the comments! 


Stavrou, A., Challoumas, D., & Dimitrakakis, G. (2014). Archibald Cochrane (1909–1988): The father of evidence-based medicine. Interactive Cardiovascular and Thoracic Surgery, 18(1), 121–124. http://doi.org/10.1093/icvts/ivt451