Tiers of Evidence: A Framework for Classifying HIV Behavioral Interventions
At the beginning of the HIV/AIDS epidemic, care providers, family members, and communities made extraordinary efforts to provide for the medical and psychological needs of their friends and families affected by HIV/AIDS. It was a new and frightening epidemic, and there were no evidence-based interventions for helping people with preventing the acquisition or transmission of HIV. In the late 1980s and early 1990s, as some early HIV treatments were developed, researchers began designing and rigorously testing HIV interventions to reduce behavioral risk of acquiring HIV infection. And after the introduction of new treatments in the mid 1990s, prevention programs with HIV-positive persons to prevention transmission of HIV became more popular.
By the late 1990s, the state of the science had developed to such a point that CDC reviewed the behavioral intervention literature and made recommendations about what interventions had evidence of reducing sex and drug injection risk behaviors. These recommendations were published in 1999 (and updated in 2001) in a document entitled “Compendium of HIV Prevention Interventions with Evidence of Effectiveness”. The Compendium represented a significant advance in the field as programs sought to implement interventions that would reduce risk in their target populations. Today the field has advanced even more, and the CDC has developed more rigorous standards for evaluating which behavioral interventions have been shown to reduce sex and drug injection risk behaviors for a variety of populations. Thus, CDC will continue to update the Compendium regularly as more evidence-based interventions are identified. The updated Compendium focuses on identifying evidence-based interventions (Tiers I and II, as described below).
The Tiers of Evidence Framework is a conceptual framework that provides a multi-tiered system for classifying all HIV behavioral interventions based on the type and level of evidence for reducing HIV risk. This framework serves the following important purposes: (1) clarifies the spectrum of interventions that may exist with various degrees of efficacy or evidence that the intervention brings about risk behavior change, (2) describes how the CDC designates evidence-based interventions (Tiers I and II) identified in the research literature, and (3) distinguishes between those interventions that have been identified in the research realm as being efficacious (Tiers I and II) and those locally-developed interventions that may be currently implemented in the prevention program field.
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, reduced HIV-related risk behaviors, reduction in HIV viral load, or improvement in HIV medication adherence 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 that need 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.
In practice, many community-based prevention providers have selected and are currently implementing DEBI interventions that fall into Tiers I and II. Other community-based prevention providers have not selected a DEBI and are implementing a locally developed intervention. Some of these locally-developed interventions fall into Tiers III and IV as well as the unevaluated intervention level.
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).
This PRS website identifies evidence-based HIV behavioral interventions (Tiers I and II interventions) and classifies them as either best-evidence (Tier I) good-evidence (Tier II) based on the level of study quality and strength of findings. Tier I and II interventions represent the updated Compendium. There are no current plans for PRS to systematically review and identify all Tier III and Tier IV interventions because there are hundreds of such interventions in the literature and many more that have been developed and evaluated, but may not have been published.
|Evidence-based Behavioral Interventions (EBIs)|
|Tier I – Best-evidence Behavioral Interventions
|Tier II – Good-evidence Behavioral Interventions have:
|Theory-based Behavioral Interventions (TBIs)|
|Tier III – Theory-based Interventions with positive outcome monitoring have:
|Tier IV – Theory-based interventions with no outcome monitoring have:
CDC encourages all HIV prevention partners, including health departments and community-based organizations, to move towards better evidence-based practice. In moving towards better evidence-based practice, this framework can be used in the following 2 ways: (1) to identify and select evidence-based HIV behavioral interventions for programmatic implementation and (2) to guide agencies delivering locally-developed interventions on how to build their evidence for their local program, as described below.
First, CDC encourages health departments and CBOs to select and implement those evidence-based HIV behavioral interventions with the strongest level of evidence, that is Tier I and Tier II interventions. These are interventions that have been scientifically shown to prevent HIV, by reducing HIV/STD incidence, reducing sex- or drug-risk behaviors, or increasing HIV-related protective behaviors. These are more likely than untested or unproven interventions to reduce HIV/STD risk when implemented in the field. Of course, the selected intervention should meet the prevention needs of the target audiences that the agency wants to address, and the agency should have the capacity to implement the intervention as it was designed and packaged. CDC recommends agencies to select and implement Tier I or Tier II interventions as is, or to adapt these interventions to fit local community needs while maintaining the core elements.
Second, for agencies delivering locally-developed interventions that want to build their evidence for their local intervention, this framework can be used as a guide to understanding where your intervention currently fits and what sort of evaluation evidence is needed to move up to the next tier. CDC suggests that agencies increase their evaluation capacity and strive for increased levels of evidence for their intervention. This means that the agency should move forward in increasing their ability to detect behavior change effects for their locally-developed intervention by moving from process evaluation (Tier IV) to outcome monitoring (Tier III). CDC recommends that agencies work with health department evaluators and researchers to understand your existing evidence and to develop and implement your next steps regarding program evaluation. CDC does not require nor expect agencies to conduct rigorous evaluations of your programs using comparison conditions, as the required funding is typically not available. Agencies are encouraged, however, to conduct adequate program evaluation, consisting of process evaluation and outcome monitoring, provided adequate funding, in order to understand how your program is working and to make improvements as needed. Finally, If developers of a locally-developed intervention want to move their intervention to Tier I or II, they should partner with local health department evaluators and researchers to conduct more rigorous research designs.