Background: Smokers attended to outpatient clinics present an excellent 'teachable moment' for smoking cessation interventions. This protocol paper describes the rationale and methods of a large randomized controlled trial which aims to evaluate the effectiveness of negotiating self-determination to reduce cigarette consumption among smokers attending outpatient clinics

Methods: A randomized controlled trial will be conducted in 10 out-patient clinics in Hong Kong. Subjects in the intervention group will receive a brief intervention on smoking reduction plus a smoking reduction leaflet. Additionally, subjects will be asked to think about a smoking reduction schedule for themselves after the negotiation with the counsellor. Subjects in the control group will receive a brief advice on quitting plus a leaflet on smoking cessation. Four consecutive (1, 3, 6 and 12 months) follow-ups will be conducted. The primary outcome measure is biochemically validated abstinence at 6 months. Secondary outcomes are: (i) biochemically validated abstinence at 12 months, (ii) self-reported 7-day point prevalence of abstinence at 6 and 12 months, (iii) self-reported reduction of ≥ 50% in cigarette consumption at 6 and 12 months, and (iv) self-efficacy against tobacco at 6 and 12 months.

This study aims to test the effectiveness of negotiating self-determination to reduce cigarette consumption (NSD-RCC) among smokers attending outpatient clinics.

Intervention Group (QP) Subjects in this group will receive a brief intervention on smoking reduction with a warning message plus a smoking reduction leaflet (the content will include a roadmap of smoking reduction strategy and information on how to cope with nicotine withdrawal symptoms). The whole intervention will last about 1 minute or slightly longer if necessary. In addition, subjects will be asked to think about a tailored smoking reduction schedule for themselves after the negotiation with the trained counsellor. For the subsequent telephone follow up in the intervention group, information on reduction and cessation will be collected, followed by a "booster" intervention, which will repeat the health warning to positively encourage them to reinforce their efforts and the next reduction target.

Control Group (QI) Subjects in the QI group will always be advised to quit immediately rather than to quit progressively. Subjects will receive a brief advice on quitting with a warning message similar to subjects in the QP group. In addition, subjects will receive a self-help quitting pamphlet published by the Hong Kong Council on Smoking and Health (COSH). Unlike the QP group, subjects in the QI group will not receive smoking reduction intervention and leaflet, and "booster" intervention during telephone follow-ups. However, they will undergo a similar schedule of telephone follow-up as those in the QP group.

Data collection

After completing the baseline questionnaire, subjects will receive proposed intervention according to their group assignment. Four consecutive follow-ups (at 1, 3, 6 and 12 months) will be conducted over the telephone by trained interviewers. Interviewers will first carry out outcome assessments with blinding to group status. Then, the group status will be disclosed so that the intervention group will receive the booster intervention and the control group will not. Smokers who have successfully quit smoking at 6-month will be invited to come back to the out-patient clinic and have biochemical validation tests (saliva cotinine test and exhaled CO test).

Analysis Data analysis will be performed using the Statistical Package for Social Science. We will compare the baseline characteristics of the participants by chi-square test for categorical variables and F-test for continuous variables between the intervention and the control group. We shall use the chi-square test to assess the effect of intervention and calculate the crude odds ratio (OR) with 95% confidence interval (CI) for the primary and secondary outcomes. Those who are lost to follow-up or refuse to participate in the validation tests, will be treated as smokers with no reduction in cigarette consumption compared with (a) baseline, as the main analysis (by intention to treat), (b) the most recent level and (c) complete case (per protocol) analysis by excluding subjects with missing data as a sensitivity analysis.

Inclusion Criteria:

smokers

• who are Chinese
• aged 18 years or above
• who smoke at least two cigarettes per day
• with moderate to severe nicotine dependence, and
• have no intention to quit smoking ≤7 days, but are interested in reducing the number of cigarettes smoked per day .

Exclusion Criteria:

smokers

• with unstable medical conditions as advised by the doctor in charge,
• with poor cognitive state or mental illness,
• who participate in other smoking cessation programmes or services,
• with mild nicotine dependence, or
• who claim that they can quit ≤7 days