Introduction: Intervention fidelity refers to whether an intervention is delivered as intended by the designer, which can affect intervention success. This study aimed to evaluate fidelity to the StepByStep approach to aphasia computer therapy delivered in the Big CACTUS trial.
Methods: A mixed methods approach was adopted comprising five interrelated studies. Firstly, a narrative literature review explored the methods used in fidelity evaluation in stroke rehabilitation research. Secondly, a qualitative interview study with StepByStep approach experts identified the key components of the intervention delivered in the Big CACTUS trial. Both of these studies informed the data to be collected in the third study, a process evaluation of intervention fidelity in the Big CACTUS trial. The fourth study explored the factors associated with adherence to computer therapy practice through secondary analysis of trial data and qualitative interviews with people with aphasia (PWA) and their carers who had used the computer therapy in the trial. The final study identified ‘essential’ components of the intervention associated with improved word-finding in the Big CACTUS trial.
Results: Key informants identified four key components of the StepByStep approach: the StepByStep software, therapy set-up (tailoring and personalising), regular independent practice, and supporting and monitoring use. All components of the intervention were delivered with moderate to high fidelity in the Big CACTUS trial. Factors associated with increased adherence to independent practice included: the PWA having had their stroke longer ago; the PWA’s perceived and actual capability to engage with computer therapy; having the opportunity to carry out practice, which was aided by having the computer therapy for longer; having more input from a speech and language therapist; and a number of motivational factors. Exploratory data analysis indicated that the components of the intervention associated with change in word-finding ability were: rigorous tailoring of the computer therapy exercises and spending more time on naming words in functional sentences exercises.
Conclusion: The StepByStep approach was delivered with moderate to high fidelity. This study has informed the interpretation of trial results, recommendations for clinicians delivering the intervention in clinical practice and will inform further intervention refinement
