Walker et al. BMC Public Health 2011, 11:37 http://www.biomedcentral.com/1471-2458/11/37 Page 6 of 8 adverse events, which occur within 30 days of disconti- nuation, will be reported to the project co-ordinator. meet two or more of the criteria stipulated by Ellenburg el al (2002), for setting up such a committee [11]. Data management The design and management of all databases associated with this trial will be undertaken by the data manage- ment and information technology groups at the Clinical Trials Research Unit. Data will be stored in the Unit’s Oracle database and linked to the electronic Case Record Form (CRF) data where applicable. Validation rules for each CRF will be specified by the project co- ordinator, in association with the senior data manager. These rules will include range checks so that inaccura- cies in data collection can be identified early. A query will be raised as soon as any values are entered that are outside the allowed range or if data are missing. The research assistants at Quitline will amend the form as soon as a query is raised. Data monitoring An independent person will monitor the trial conduct. This monitor will audit Quitline and the Clinical Trials Research Unit during the trial to ensure that the study protocol is being adhered to. At Quitline the monitor will audit every randomised participant’s records to ensure their existence, that they meet the inclusion cri- teria and have provided informed consent, and that the treatment is being distributed within the limits of the protocol. The monitor will review the study documenta- tion and records held by Quitline to ensure that docu- mentation is up-to-date and record keeping meets the requirements specified in the protocol and complies with regulatory requirements. The monitor will visit Quitline early on during the study (after ten participants have been randomised), at study close-out and twice during the course of the trial. The monitoring task for the trial is unlikely to be onerous as the majority of data for this trial will be collected electronically, with range and logic checks built into the programme used. In the rare event that the computer programme is not accessi- ble (e.g. power cut, system down), hard copies of the CRF’s will be completed by the research assistants at Quitline, with the data entered onto the Unit’s computer database at a later stage. Hard copies of the CRF’s will be checked for consistency by the monitor and checked against the electronic copy. The monitor will audit the Unit every three months to see that the product supply records are in order and that there are sufficient sup- plies remaining, that the nicotine-free cigarettes are being stored appropriately and that the handling of unused nicotine-free cigarettes complies with study pro- cedures. A Data Safety and Monitoring Committee has not been established for this trial as the trial does not Data analyses This trial has been designed with the assistance of a senior statistician at the Clinical Trials Research Unit, who will continue to advise and assist with analyses of the trial data. Treatment effects Analyses will be undertaken on an intention-to-treat basis, according to a pre-specified statistical analysis plan using SAS version 9.1.3. A per-protocol analysis will also be performed in order to check the robust- ness of the results. No interim analysis will be underta- ken. Chi-squared analyses will be used to compare the proportion quit by treatment group, and incidence rates, relative risks, risk differences, 95% confidence intervals and two-sided p-values will be calculated. Logistic regression analyses will be utilized to adjust for important prognostic factors. Continuous outcome data will be analysed using multiple linear regression modelling. Both the number of cigarettes per day and withdrawal symptoms over time will be compared using analysis of covariance. Pre-specified subgroup analyses using tests for heterogeneity will be underta- ken for ethnicity (Māori, non-Māori), age (< 40 years, ≥ 40 years), sex and socioeconomic status (dichoto- mised as those who left school below Year 12 or with no school qualification, and those who completed Year 12 and above). Analyses will also be undertaken to examine time-to-first-lapse using Kaplan-Meier analy- sis and self-reported seven-day point prevalence of smoking abstinence at six months in those with com- plete smoking status data. Cost analyses Costs analyses will be undertaken if a statistical differ- ence between the groups is observed for the primary outcome of interest. Cost outcomes will include cost per quitter, cost per person reducing their daily cigar- ette consumption, and cost per quality adjusted life year of life saved among quitters (using discount rates of 0%, 5% and 10%). These data will then be compared with New Zealand data from Quitline and other NRT service providers, in addition to information from var- ious international studies. This modelling will take a health sector perspective. However, the tobacco expen- diture savings to individual smokers will also be calcu- lated (for those who quit and cut down) to give a more societal perspective on the benefits (especially to low-income smokers). This calculation will use data on the daily amount smoked prior to quitting and the price of the particular products smoked. For those who cut down their consumption by a significant margin