EBDM Basic Concepts

In order to use an evidence-based approach, understanding evidence-based concepts involves knowing the design of different research methods.

EBDM is comprised of 4 elements: clinical expertise, patient preferences, clinical circumstances and the scientific evidence. EBDM is a tool to improve the quality of care and to reduce the gap between what we know and what we do. EBDM is about solving clinical problems. In solving these problems, a hierarchy of evidence is available to guide clinical decision-making and as a hierarchy implies, not all evidence is equally useful for making patient care decisions.

As you progress up the hierarchy, the research designs allow more control so that intervention or treatment outcome differences are not due to chance. Also, as you progress up the hierarchy, the number of published studies decreases, and yet these are more clinically relevant studies. Therefore, to answer your question, you should search for studies at the top of the hierarchy, (e.g., Practice Guidelines, Meta-analyses, Systematic Reviews, and then RCTs).

There are two categories of evidence sources: Primary and Secondary research studies (Figure 8). Primary research is the original, individual study. The highest level of primary research is an individual randomized controlled trial (RCT), Level 1. Primary studies involve participants that undergo an intervention or receive a treatment in order to evaluate its impact and are the most complex to conduct. RCTs provide the strongest evidence for demonstrating cause and effect, i.e., the treatment (e.g., type of electric toothbrush) has caused the effect (decrease in gingivitis), rather than it happening by chance.

Figure 8. Hierarchy of Evidence.

Figure 8. Hierarchy of Evidence.

©2008 Forrest & Miller, NCDHR Source: DHNET. Research & Topics

Categories of Research Designs: Primary and Secondary research studies and how they relate to the hierarchy of evidence.

Secondary research is a synthesis of primary research providing a higher level of evidence by including summaries of at least two individual studies on the same topic, e.g., Systematic Reviews (SRs). (Figure 9). This scientific technique defines a specific question to be answered and uses explicit pre-defined criteria for retrieval of studies. An example of a specific question is, “For adult patients with heavy plaque, will electric toothbrush A, as compared to electric toothbrush B, be more effective in decreasing the amount of plaque over a 3-month period?”

Figure 9. Relationship between Primary and Secondary Research.

Figure 9. Relationship between Primary and Secondary Research.

Source: DHNET. Research & Topics

Summary of Relationship between Primary and Secondary Research.

Methods used in SRs parallel those of RCTs in that they follow rigorous procedures and each step should be thoroughly documented and reproducible. For example, where individual RCTs have predefined criteria for the inclusion and exclusion of subjects, SRs have predefined criteria for the inclusion and exclusion of research studies. A SR with a Meta-Analysis, often referred to as just a meta-analysis (MA), combines the data from similar individual studies and conducts an analysis of this pooled data.

Systematic reviews and MAs serve as the basis for formulating Clinical Practice Guidelines (CPGs), which sit at the top of the hierarchy. One of the challenges of the evidence-based process is interpreting the research and appraising the results, a CPG does just that. It is not a research design, but the interpretation of the research so that it can be applied to patient care. Although SRs and MAs are higher levels of evidence, the systematic reviews are only as good as the individual studies that are included, therefore, not all are created equal.