Table 1 Conceptual framework for implementation fidelity used in this review

 Content

Defined as an attempt to establish the “active ingredients” of the intervention, for example, in a theory of change or logic model, and assess whether they have been delivered as planned

 Coverage

Refers to the degree to which all persons who met study inclusion criteria received the intervention

 Frequency

Refers to whether the intervention was delivered with the regularity or frequency planned by its designers.

 Duration

Establishes whether the intervention was delivered with the duration planned by its designers.

 Comprehensiveness of intervention description

Factors such as the degree of intervention complexity and whether the intervention description is complete or incomplete, vague, or clear may influence the degree of implementation fidelity.

 Strategies to facilitate implementation

Several support strategies may be used to optimise and to standardise implementation fidelity.

 Quality of delivery

Concerns whether an intervention is delivered in a way that increases the likelihood of achieving the desired health outcomes

 Participant responsiveness

Intervention uptake depends on its acceptance by and acceptability to those receiving it. Low participant involvement or responsiveness may negatively impact intervention fidelity.

 Recruitment^a

Refers to procedures that were used to attract potential programme participants.

 Context^a

Refers to the surrounding social systems, such as structures and cultures of organizations and groups, and historical and concurrent activities and events