Fidelity Assessment in Implementation

Fidelity Assessment is the systematic measurement of the degree to which an intervention is delivered as designed in real-world practice. Formalized by the National Institutes of Health Behavior Change Consortium (Bellg et al. 2004) and expanded in MRC guidance (Moore et al. 2015), fidelity assessment is critical to implementation science because it answers: 'Did we deliver the intervention correctly?' A clinical trial may show a treatment works, but if delivered poorly in practice, benefits disappear. Fidelity assessment prevents misattribution of failure (was the intervention weak, or was implementation poor?) and guides coaching to improve quality.