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How Do We Decide?

Rigorous assessments, such as multiple randomized clinical trials, consensus reviews of available science, or expert opinion based on clinical observation, are conducted to identify such practices. Practices that are subjected to less rigorous review are sometimes called promising practices or best practices.3

According to SAMHSA, “other methods of establishing evidence are considered valid as well. Evidence-based practice stands in contrast to approaches that are based on tradition, convention, belief, or anecdotal evidence.” 

The Centers for Disease Control and Prevention have created “The Tiers of Evidence Framework”  which illustrates the many layers of evaluation.

The Tiers of Evidence Framework


Tiers I and II comprise the evidence-based interventions, because they are based on direct, high-quality, empirical evidence that demonstrates a reduction in HIV/STD incidence or reduced HIV-related risk behaviors. Tiers III and IV comprise the theory-based interventions, which are based on sound behavioral science theory, but do not have sufficient empirical evidence to satisfy CDC criteria for evidence-based interventions. These interventions, however, do have some empirical evidence in the form of process data or outcome monitoring data. A brief description of the criteria needed to be satisfied for an intervention to be classified into one of these four tiers is presented in the Tiers of Evidence Table. The lowest category in the Tiers of Evidence diagram, “unevaluated interventions,” represents all other interventions that may still exist but have never really been evaluated.

The graphic below illustrates that Tier I and II interventions are at the top of the pyramid indicating they are currently included in the category of strongest evidence, while interventions on the bottom represent those that have never been evaluated and have no evidence. This framework also acknowledges the current state of the science and prevention field by having the size of each tier represent the existing number of interventions within each tier (i.e., currently there are a large and unknown number of existing interventions that have never been evaluated, while there are a smaller number of interventions identified as evidence-based (Tier I or Tier II) interventions).

The Tiers of Evidence Framework

The Tiers of Evidence Framework



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