Outcomes
AIDS
The primary outcomes were prolonged abstinence and point prevalence of smoking abstinence, measured at 3 and 6 months post-randomisation. Prolonged abstinence was defined following the Russell standard [Secondary outcomes were 7-day point prevalence of smoking abstinence, number of cigarettes smoked weekly (if still smoking), number of quit attempts since baseline, and number of uses of other smoking-cessation aids since baseline.Three potential mediating factors were assessed: importance, confidence, and knowledge of how to quit (know-how). To reduce participant burden across the entire trial period, we decided against using multi-item questionnaires to measure these factors, instead relying on face valid single-item measures based on importance and confidence rulers [Items used to assess three potential mediatorsThere were three follow-up intervals: 1, 3, and 6 months post-randomisation. At the 1-month follow-up, the three hypothesised mediators were assessed only. All follow-ups were initiated by sending text messages to participants with hyperlinks to questionnaires. In all cases, the following additional attempts were made to collect data:A total of 2 reminders were sent 2 days apart.If no response was given to (1), then questions were sent directly in a text message, asking participants to respond directly with a text (no hyperlink). We only asked for primary outcome measures at this stage.If there was no response given to (2) at 3 and 6 months, we attempted to call participants to collect primary outcomes. A maximum of 5 call attempts were made.