JMIR Publications

ABSTRACT

Background:

The National Health Service (NHS) Diabetes Prevention Programme is a behaviour change intervention for adults in England who are identified as being at high risk of developing Type 2 diabetes. The face-to-face service was launched in 2016, followed by a digital service (NHS-DDPP) in 2019 to extend access to the programme. Four service providers were commissioned to deliver the NHS-DDPP and required to deliver the digital service in line with a programme specification detailing key intervention content. The fidelity of the behaviour change content in the digital service (i.e. the extent to which the programme is delivered as intended) is currently unknown. Digital interventions may allow higher fidelity as staff do not have to be trained to deliver all intervention content. Assessing fidelity of intervention design is particularly important to establish the planned behaviour change content in the NHS-DDPP and the extent to which this adheres to the programme specification. This is the first known independent assessment of fidelity of design in a large-scale digital behaviour change intervention.

Objective:

To assess fidelity of the behaviour change content in each of the four NHS-DDPP providers’ intervention designs to the full programme specification.

Methods:

We conducted a document review of each providers’ NHS-DDPP intervention designs, alongside interviews with programme developers employed by each of the four digital providers (n = 6). Providers’ intervention design documents and interview transcripts were coded for: behaviour change techniques (BCTs, i.e. the ‘active ingredients’ of the intervention) using the Behaviour Change Technique Taxonomy v1; and underpinning theory, assessed using the Theory Coding Scheme framework. The BCTs identified in each digital providers’ intervention designs were compared with the 19 BCTs included in the programme specification.

Results:

Overall, providers planned to deliver 16, 17, 16 and 16 (85%) of 19 BCTs specified in the programme specification. An additional 41 BCTs not specified were included in at least one of the four digital providers’ intervention designs. By contrast, inconsistent use of underpinning theory was apparent across providers and none of the providers had produced a logic model to explain how their programmes were expected to work. All providers linked some of their planned BCTs to theoretical constructs (e.g. goal setting and social support linked to self-efficacy), but justification for inclusion of other BCTs was not described.

Conclusions:

Fidelity of BCT content in the NHS-DDPP was higher than that previously documented for the face-to-face service. Thus, if service users engage with the NHS-DDPP, this should increase the effectiveness of the programme. However, given that a clear theoretical underpinning supports the translation of BCTs in intervention designs to intervention delivery, the absence of a logic model describing the constructs to be targeted by specific BCTs is potentially problematic.