Effectiveness of an App for Tobacco Cessation in Pregnant Women (TOBBGEST)

Design: community-based intervention trial with simple random assignment.

Setting and study population: the study population will be drawn from the usual consultations of 4 Sexual and Reproductive Health Care Centres (ASSIR) responsible for pregnancy monitoring in the community, managed by the Catalan Health Institute (ICS) in Tarragona and Barcelona.

Study subjects: pregnant women over 18 years of age who attended the ASSIR services and consented to participate in the study and meet the inclusion criteria.

Randomisation process of the intervention: the participants included will be assigned to receive or not to receive the proposed intervention. The allocation sequence will be carried out consecutively, centralised from the Research Support Unit of the Jordi Gol Primary Care Research Institute in Tarragona, following a simple numerical randomisation ratio. No masking will be possible either for pregnant women or for ASSIR professionals; the data will be masked for the research team carrying out the statistical analyses.

Selection of the participating centres: the pregnancy monitoring centres participating in the recruitment of the study will be four, all of them from the ICS. Three in the Tarragona region (Tarragona, Reus and Valls) and a fourth in the Osona region of Barcelona (Manresa).

Intervention: ASSIR centre will offer treatment, following the standard practice protocols, to all participants who want to quit smoking, following standard practice protocols. Additionally, only participants assigned to the intervention group will have the access code to the Tobbstop App (www.tobbsotop.com) and its use will be recommended. The quality of the intervention will be assured by a three-level control system:

1. Adaptation of the App. The Tobbstop App has been successfully tested in the general population. For the present study the contents will be updated and adapted to the study population (pregnant women). In that sense, a qualitative study will be carried out with the aim of identifying the facilities and barriers that pregnant women face to stop smoking through individual interviews and focus groups.
2. Technical training. Training will be carried out in each of the centres participating in the pregnancy control follow-up visits. The training will be performed by health professionals in order to understand the use of the App.
3. Centralised monitoring. Confirmatory tests will be referred to a single reference observer who will centralise quality control and interpret the results (urinary cotinine).

Follow-up: no additional follow-up visits will be planned for the study. In the scheduled pregnancy follow-up visits, smoking habits will be assessed by a questionnaire and CO level quantification by coximetry. At the end of the pregnancy check-ups, follow-up will be carried out by telephone contact. Women who quit smoking will be scheduled to visit their health centre 12 months after the intervention to find out about their relationship with smoking. If they report abstinence, a coximetry test will be performed and if it is less than 10 ppm (\&), urinary cotinine will be determined.

(\&) The cut-off point is considered to be 10 ppm, as lower values indicate non-smoking and higher values indicate smoking in the previous 12-24 hours.

Data recording: the information from the study will be recorded in a structured way by a data collection questionnaire and will be stored in an application accessible from the corporate Intranet of the Catalan Institute of Health. Access to this website is restricted and will be controlled by a personal password for each researcher, who will be responsible for entering the records of the participants recruited.

Definition of the outcome variable: prolonged abstinence from drug use will be considered as the main variable, and punctual abstinence as a secondary variable, both validated by biochemical confirmation 12 months after the intervention. Urine cotinine values less than 100ng/ml will reflect an abstinence condition, values between 100 and 500 ng/ml will be accepted as occasional smoker, and values above 500ng/ml will be considered as smoker.

The criteria for establishing abstinence according to the recommendations of the Society for Research on Nicotine and Tobacco:

• Continuous abstinence: sustained abstinence from the time of intervention to a follow-up period.
• Prolonged abstinence: sustained abstinence between an initial grace period ($) and a follow-up period.
• Punctual abstinence: abstinence during a window of time (usually 7 days) immediately preceding the time of follow-up. ($) Grace period is the period immediately following the defined quit date or intervention date in which continued smoking is not counted as failure. For most studies it is recommended to be no longer than 2-4 weeks.

In general, continuous abstinence is accepted as the gold standard. However, this measure is too stringent and prolonged abstinence is preferred as it includes the participants who achierve sustained abstinence after a transitional grace period, which would otherwise be considered failures.

Sample calculation: accepting an alpha risk of 0.05 and a beta risk of less than 0.2 in a bilateral contrast, it will be necessary to include 200 participants in each group, in order to detect the difference between the two proportions statistically significant. In the control group is expected to be 0.5 and in the intervention group 0.65. A loss-to-follow-up rate of 5% is estimated. The ARCSINUS approximation (GRANMO Sample Size Calculator v.7.12 available at www.imim.es) was used.