Table 1.

Outcome variables and associated measures.

Variable	Measure
Acceptability, usability, and satisfaction of the chatbot, including the risk assessment dialogue and follow-up dialogues on asthma triggers and management strategies for improvement of asthma control	We will combine the following standard technology satisfaction measures: Task completion (% complete risk assessment process vs drop-out rate) Net Promoter Score question: “how likely are you to recommend the chatbot to someone else with asthma on a scale from 0 to 10” User satisfaction questions for each dialogue topic (eg, “Did you measure your risk using the chatbot? How useful did you find this feature?”) Open-ended questions on what worked well and what did not, and how the chatbot could be improved
Motivational quality, engagement, and user experience in relation to basic psychological needs	Motivation, Engagement, and Thriving in User Experience questionnaire [14]
Alignment between expected and calculated risk, and whether the calculated result changes risk self-assessment	Self-report questions on risk score expectation vs result and trust in result
Changes to asthma understanding, attitudes, and behaviors following use of the app	Self-report questions on changes to understanding, attitudes, and behaviors related with asthma self-management
Self-reported level of asthma control and symptoms, including changes over time	The Asthma Control Questionnaire [20] will be asked at the beginning and end of the study
Patterns of engagement and satisfaction for different types of users, particularly those who do not access professional services and those with poor asthma control	Analysis of pre- and postquestionnaires and additional self-report questions on use of professional services (eg, “when was the last time you spoke to a GP about asthma”)