Send to

Choose Destination
Addiction. 2019 Sep 8. doi: 10.1111/add.14804. [Epub ahead of print]

Measuring fidelity to behavioural support delivery for smoking cessation and its association with outcomes.

Author information

University of York, Department of Health Sciences, Heslington, YO10 5DD, York, UK.
The University of Edinburgh, Usher Institute, EH8 9AG, Edinburgh, UK.
University of Dundee, School of Nursing and Health Sciences, DD1 4HN, Dundee, UK.
University College London, Centre for Behaviour Change, WC1E 6BT, London, UK.
University of York, Hull York Medical School, Heslington, YO10 5DD, York, UK.



Behavioural support increases smoking cessation in clinical settings, but effect sizes differ among providers, possibly due to variations in delivery. This study evaluates a measure ("fidelity index") intended to capture fidelity to delivery of content-based and interaction-based items of a Behavioural Support (BS) for smoking cessation and the association of fidelity with quit rates.


A fidelity index for scoring the adherence and quality domains of a specific BS intervention, 5As for quit, was developed by classifying the intervention components using the taxonomy of Behaviour Change Techniques. The index was applied to code 154 BS sessions audiotaped across 18 chest clinics in Pakistan to assess their fidelity and explore reliability of coding. The association between intervention fidelity and successful quit achieved by the same providers in a previous study was explored using regression analysis.


The index represented two domains: adherence to delivery of content-based activities of 5As (37 items) and quality of interaction-based activities (8 items). The inter-coder reliability was good for content-based (average Krippendorff's α = 0.80) and moderate for interaction-based (average Krippendorff's α = 0.66) items. About 70% (Intra-class Correlation Coefficient: adherence scores = 0.72, quality scores = 0.71) of variation in BS delivery was contributed by providers, which increased to 97% (g-coefficient: adherence scores = 0.973, quality scores = 0.974) after accounting for other sources of variation. Higher quit rates were positively associated with average quality scores (risk ratio: 2.15; 95% CI, 1.43 to 3.24), but negatively associated with average adherence scores (risk ratio: 0.55; 95% CI, 0.40 to 0.77), within services.


The fidelity index is a reliable measure for quantifying intervention fidelity of delivering smoking cessation behavioural support. Recommended revisions of the fidelity index include incorporation of additional interaction-based items, like the relational techniques used in motivational interviewing.


Behaviour Change Techniques; Behavioural Support; Fidelity Index; Fidelity scores; Intervention fidelity; Smoking cessation


Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center