Table 4.

Features of engagement and measuring methods (N=16).

Study	Theory of engagement	Features of engagement	Tool used to measure engagement
Lappalainen et al, 2013 [15]	Technology tools	Affect	Questionnaire on perceived utility and acceptance
Lappalainen et al, 2013 [15]	Technology tools	Frequency	Automatic+questionnaire and number of log-ins
Todkill and Powell, 2013 [16]	—a	Affect, attention, and interest	Interviews on content, medium, functionalities, and experience
Morris et al, 2015 [17]	Technological interaction and consumption	Attention, interest, and depth	UEQb+interview
Morris et al, 2015 [17]	Technological interaction and consumption	Amount, duration, and frequency	Automatic; time per session, time of intervention use total, and number of log-ins
Clarke et al, 2016 [18]	—	Affect	Interview
Clarke et al, 2016 [18]	—	Frequency	Automatic; number of log-ins, number of modules completed, frequency of self-monitoring, and interviews
Laurie and Blandford, 2016 [19]	—	Affect, attention, and interest	Interview and qualitative interviews
Laurie and Blandford, 2016 [19]	—	Frequency	Automatic; frequency of app use over study period
Zarski et al, 2016 [20]	—	Duration and frequency	Automatic; number of completed modules
Chou et al, 2017 [21]	—	Interest, depth, duration, and frequency	Automatic; completion rate of intervention
Dryman et al, 2017 [22]	Motivational techniques delivered by coaches	Frequency and duration	Automatic; average number of days in the program, average activities per participant, and completion rate of all modules
Ly et al, 2017 [23]	Fully automated conversational agent	Affect, attention, and interest	Interview
Ly et al, 2017 [23]	Fully automated conversational agent	Frequency	Automatic; number of reflections completed, number of active days, open app ratio, and interviews on content, medium, and functionalities
Bakker et al, 2018 [24]	Recommendations by Bakker et al [31] (2016)	Affect, attention, interest, depth, and frequency	Questionnaire, uMARSc, text-entry questions, and HRS-MAd
Morrison et al, 2018 [25]	Recommendation by Dennison et al [32] (2013)	Affect and attention	Questionnaire on satisfaction with the intervention, PEIe, and TAM-2f
Morrison et al, 2018 [25]	Recommendation by Dennison et al [32] (2013)	Duration and frequency	Automatic; total time of intervention use, time per log-in, and number of log-ins
Song et al, 2018 [26]	—	Interest, amount, duration, and frequency	Automatic; number of pages accessed per session, time per session, goal conversion rate, number of returning users, bounce rate, and number of pages accessed per session
Birk and Mandryk, 2019 [27]	Self-determination theory	Attention	Questionnaire and Player Identification Scale
Carter et al, 2019 [28]	Patient engagement framework	Frequency, attention, and interest	Automatic+questionnaire; percentage of task completion per user, average completion time of tasks, average CSATg scale score, Nielsen–Shneiderman heuristics, and SUSh
Przybylko et al, 2019 [29]	Experiential pedagogical framework	Duration	Automatic; attrition rate
Renfrew et al, 2020 [30]	SAMi	Duration Frequency	Automatic; total duration of videos viewed, number of videoconference sessions attended, and challenge score

^aNot available.

^bUEQ: User Experience Questionnaire.

^cuMARS: Mobile Application Rating Scale, user version.

^dHRS-MA: Homework Rating Scale-Mobile Application.

^ePEI: Patient Enablement Instrument.

^fTAM-2: Technology Acceptance Model-2.

^gCSAT: Customer Satisfaction.

^hSUS: System Usability Scale.

ⁱSAM: Supportive Accountability Model.