NCT02840513.

Trial name or title	Smartphone App and CO Self‐monitoring for Smoking Cessation (SMART‐CO)
Methods	Parallel‐group, open‐label randomised controlled trial
Participants	510 participants, 16 years of age and older Inclusion criteria: HIV‐infected smokers 16 years and older smoking 3 cigarettes per day enrolled into the Swiss HIV Cohort Study Willingness to quit smoking Speaking 1 or more of official Swiss national languages or English users of smartphone (specifically iPhone 5, 5c, 5s, 6, 6+ running iOS version 8.0+; smartphones with resolution of at least 800 x 400 pixels running Android version 5.0+; and Android smartwatches) Informed consent Exclusion criteria: Limitations in hearing, comprehension, or vision problems that preclude full study participation Participants with a life expectancy of less than 12 months due to any serious medical condition
Interventions	The app offers a coaching function where users receive personalised messages to encourage smoking cessation and advice for behavioural changes. For the first 4 weeks of the intervention, individuals will also be asked to blow daily into a breath carbon monoxide monitor before going to sleep. Depending on the results of the breath test, individualised messages will be delivered by the Smokelyzer feedback app to either enhance maintenance of abstinence or to increase the motivation to quit. After the first 4 weeks, participants will use the breath carbon monoxide monitor at least twice a week until the end of the 6‐month study. The app will react with positive feedback in individuals doing well with smoking cessation and messages to encourage individuals with difficulties quitting smoking.
Outcomes	Primary outcome measures: Self‐reported abstinence biochemically verified by a carbon monoxide test in‐person. (Time Frame: 6 months) Secondary outcome measures: Differences in the number of daily cigarettes smoked from baseline to 6‐month follow‐up and point prevalence of abstinence (i.e. no smoking in the past 7 days) at 6‐month follow‐up. (Time Frame: 6 months)
Starting date	1 June 2017
Contact information	Dmitry Gryaznov dmitry.gryaznov@usb.ch
Notes	Estimated study completion date: 1 July 2019