Introduction:
In many countries smokers have limited access to evidence-based stop smoking support. Moreover, even in countries were such support is offered free at the point of access, such as the UK, only 5% of smokers use it. This necessitates development of new methods for intervention delivery. Smartphone applications (apps) are a new possible medium for providing behavioural cessation support. However, very limited research exists on their effectiveness and acceptability, and we are still in the process of establishing best practice methods for creating and assessing such interventions. The steps taken in the process of evaluating two stop smoking apps were documented to identify methodological challenges and potential solutions.

Material and Methods:
Between 2014-2016 we developed and subsequently conducted mixed-methods evaluations of two app supporting UK-based smokers wanting to quit. One of these focused on craving management, and the other on supporting adherence to nicotine replacement purchased over the counter. These two interventions were evaluated through pragmatic feasibility two-arm parallel randomized controlled trials (RCTs) embedded within the apps that were live on app stores, and subsequently through qualitative interviews.

Results:
Conducting a randomized controlled trial of smartphone apps that are live on app stores was feasible. However, several challenges to evaluation were identified, including selection of appropriate control arms, study promotion, data collection and management, and remote verification of smoking status. Considerable resources were required to support recruitment, eligibility check, and follow-ups outside of the app. Close collaboration with IT partners throughout the project is vital. Finally, qualitative interviews offered valuable insights to interpret quantitative data, but also to inform future evaluation of apps.

Conclusions:
Evaluating stop smoking apps through randomized controlled trials is feasible, but has important methodological and practical challenges that have to be factored in from early on during project planning and budgeting.

Funding:
AH is funded by British Heart Foundation PhD Studentship at University College London. The costs of conducting BupaQuit trial have been funded by Bupa. NRT2Quit trial was funded through Global Research Awards for Nicotine Dependence (GRAND) Program by Pfizer.