Does the design of the NHS Diabetes Prevention Programme intervention have fidelity to the programme specification? A document analysis.

There is good fidelity to the specified service parameters of the NHS-DPP; however, the four providers planned to deliver approximately three-quarters of behaviour change techniques specified by the NHS-DPP. Given that behaviour change techniques are the 'active ingredients' of interventions, and some of these techniques in the programme manuals may be missed in practice, this highlights possible limitations with fidelity to the NHS-DPP programme specification at the intervention design stage.