Haug 2013.

Methods	Study design: cluster‐RCT Country: Switzerland Recruitment: from students in vocational schools Study dates: 2011‐12
Participants	Baseline characteristics (n = 755) Mean age: 18.2 years (SD 2.3) Female: 51.9% (N = 392) Secondary school or less: 81.6% (N = 616) Cigarettes per day mean: 10.6 (SD 7.6) No immigration background: 53.2% (N = 399) Inclusion criteria: daily or occasional cigarette smoking (at least 4 cigarettes in the preceding month and at least 1 cigarette during the preceding week), ownership of a mobile phone Exclusion criteria: not explicitly stated
Interventions	SMS‐COACH: a 3‐month programme including a weekly SMS text message assessment of smoking‐related target behaviour, 2 weekly text messages tailored to baseline data and responses to the SMS text message assessments, and an optional further integrated QD preparation and relapse prevention SMS programme. Participants who did not use the integrated programme for QD preparation and relapse prevention received a total of 37 text messages (1 welcome message, 11 assessment messages, 24 tailored feedback messages, 1 goodbye message). Participants, who used the QD preparation and relapse‐prevention programme for the whole period from 1 week before the scheduled QD until 3 weeks afterwards, received an additional 42 text messages Control: all students in participating classes were invited to participate in an online health screening survey during a regular school lesson reserved for health education. The control group did not receive anything else
Outcomes	Definition of abstinence: self‐reported 4‐week point prevalence abstinence at 6‐month follow‐up
Funding source	Swiss Tobacco Prevention Fund
Conflicts of interest	SH and CM were involved in the development of the intervention
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Block randomisation with computer‐generated randomly permuted blocks of 4 cases
Allocation concealment (selection bias)	Unclear risk	No information provided
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Minimal contact with study investigators in both trial arms
Incomplete outcome data (attrition bias) All outcomes	Low risk	111/383 in control and 85/372 in intervention were lost to follow‐up at 6 months. ITT analysis conducted
Other bias	Unclear risk	Although clustering is adjusted for in this study's analysis the authors do not report the clustering effect, making it impossible to adjust for this in our analysis. Therefore, it is not clear how much the clustering adjustment influences the result from this study.