Fidelity is the degree to which an intervention is implemented as its original developer intended. Interventions that are implemented with fidelity are more likely to replicate the results from the original intervention than are those that make substantial adaptations. Training on how to implement the intervention, especially if it’s available from the program developer, will increase your ability to implement with fidelity.
That being said, at times it may be necessary to adapt the intervention to better fit your local circumstances or meet your needs. For example
- Your target population may be different in some way from the population that was originally evaluated
- Some intervention elements may need to be adjusted due to budget, time, or staffing restraints
Balancing fidelity and adaptation can be tricky, since any time you change a strategy or intervention, you may compromise the outcomes. Even so, implementing an intervention that requires some adaptation may be more efficient, effective, and cost-effective than designing a new one.
Some general guidelines for adapting an intervention:
- Select strategies with the best initial fit to your local needs and conditions. This will reduce the likelihood that you’ll need to make adaptations later.
- Select strategies with the largest effect size—the magnitude of a strategy’s impact. For example, policy change generally has a larger effect size than a classroom-based program. The smaller a strategy’s effect size, the more careful you need to be about changing anything, since you don’t want to inadvertently compromise any good that you are doing. In general, adaptations to strategies with large effect sizes are less likely to affect relevant outcomes.
- Implement the strategy as written before making adaptations, since you may find that it works well without having to make changes.
- When implementing an evidence-based intervention, consult with the intervention developer before making adaptations. The developer may be able to tell you how the program has been adapted in the past and how well these adaptations have worked. If the developer is not available, work with an implementation science expert or your evaluator.
- Retain the core components, since there is a greater likelihood of effectiveness when an intervention includes these components. If you aren’t sure which elements are core, refer to the intervention’s logic model, if it is available, or consult the program developer or your evaluator for assistance.
- Stick to evidence-based principles. Strategies that adhere to these principles are more likely to be effective, so it is important that adaptations are consistent with the science.
- Adjust your coalition’s capacity before you adapt an intervention. While it may be easier to change the intervention, changing local capacity to deliver it as it was designed is a safer choice.