Outputs and moderating factors
Outputs are the activities undertaken when implementing a behaviour
change intervention (8, 9). Historically, evaluation has focussed on the
intervention’s effectiveness without evaluating fidelity (9). Fidelity
is the degree to which an intervention is implemented as intended. It is
essential for interpreting whether the observed outputs are a faithful
measure of intervention effectiveness. Guidance for process evaluations
of complex interventions emphasises the importance of evaluating
fidelity, but does not provide recommendations regarding how to do it.
Several frameworks are available to guide fidelity evaluation; however,
they are frequently not adopted in trials of behaviour change
interventions (9).
Evaluating fidelity has historically focussed on dose andreach, whereas fidelity of delivery, receipt and enactment are
now recognised as important (9). The Conceptual Framework for
Implementation Fidelity (8) measures four components of fidelity:
content, coverage, frequency and duration of the intervention. It also
captures four moderators of fidelity: intervention complexity,
facilitation strategies, quality of intervention delivery and
responsiveness of participants (8). By comprehensively capturing
fidelity of each intervention component, it can also be determined which
are essential to achieving the desired change in behaviour. Any
adaptation or flexibility of intervention delivery should also be
captured to understand how sites implement an intervention component(s)
and how this variation impacts the intervention’s effectiveness.