Although there is an increasing recognition of, and attention to, the importance of fidelity, there is still a lack of clarity in the definition and operationalization of this construct. Moreover, there is inconsistency in the methods employed for measuring fidelity, and fidelity results are rarely reported in publications of behavioral intervention research. Nevertheless, it is clear that the cost of low fidelity is substantial and may include the rejection of an effective program, the acceptance of an ineffective program, or the inability to replicate a program.
As discussed, fidelity has a different role depending upon the phase of development of a particular intervention. In development phases, attention to fidelity enables an evaluation of the feasibility of implementation; whereas, in the evaluation phases, attention to fidelity helps to optimize an understanding of treatment outcomes and whether a desired outcome is due to the intervention itself or the way it was implemented, or if other potential factors are responsible for outcomes. Its role further changes in the implementation phases; here, fidelity becomes an important outcome in its own right (Proctor et al., 2011) and serves as a key indicator of the replication potential of the intervention. However, the role of fidelity and how fidelity plans are implemented when seeking to sustain an intervention are not clear and remain uncharted.
As an intervention is being developed, evaluated, and implemented, careful attention needs to be given to fidelity. Specifically, attention should be given to three activities: enhancing, monitoring, and measuring four components that are study design, and the delivery, receipt, and enactment of the intervention itself. The level of complexity of a fidelity plan that is executed will reflect several factors: the phase of intervention development, purpose of fidelity, the characteristics of the intervention itself (e.g., its treatment components, dosage, and activities), financial and staffing resources, and intricacy of the study design (e.g., type of control group employed). As addressing fidelity requires resources, fidelity plans can be challenging to implement. At a minimum, some form of tracking of study design and intervention processes is critical to provide a level of assurance that an intervention is being delivered as intended.