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. 2015 Oct 1;5(10):e008807. doi: 10.1136/bmjopen-2015-008807

Table 2.

Quality of the randomised clinical trials included in the review, based on SIGN guidelines (continued on following page)

Ítem Daughton et al (1998) Grandes et al (2000) Torrecilla et al (2001) Twardella et al (2007) Secades-Villa et al (2009)
1. The study addresses an appropriate and clearly focused question? Yes Yes Yes Yes Yes
2. The assignment of participants to treatment groups is randomised? Yes No Yes Yes Yes
3. An adequate concealment method is used Yes Yes Can't say Can't say Can't say
4. Participants and investigators are kept ‘blind’ about treatment allocation Yes No Can't say No Can't say
5. The treatment and control groups are similar at the start of the trial Yes Yes Yes Yes No
6. The only difference between groups is the treatment under investigation Yes Yes Yes Yes Yes
7. All relevant outcomes are measured in a standard, valid and reliable way Yes Yes Yes Yes Yes
8. What percentage of the individuals or clusters recruited into each treatment arm of the study dropped out before the study was completed? 1.1% at 3 months, 1.6 at 6 months and 2.2% at 1 year Control group: 1.8%
Intervention group: 4.6%
CG: 6%
Isolated advice :3%
NRT: 7.7%
CG:19%
The interventions 14–17%
1.2%
9. All the participants are analysed in the groups to which they were randomly allocated (often referred to as intention-to-treat analysis) Yes Yes Yes Yes Yes
10. Where the study is carried out at more than one site, results are comparable for all sites Yes Yes Does not apply Yes Does not apply
11. How well was the study done to minimise bias? Acceptable Acceptable Acceptable Acceptable Acceptable
12. Taking into account clinical considerations, your evaluation of the methodology used, and the statistical power of the study, are you certain that the overall effect is due to the study intervention? Yes Yes Yes Yes Yes
Ítem Ramos et al (2010) Cabezas et al and Puente et al (2011) Lou et al (2013) Smit et al (2013)
1. The study addresses an appropriate and clearly focused question? Yes Yes Yes Yes
2. The assignment of participants to treatment groups is randomised? Yes Yes Yes Not clear
3. An adequate concealment method is used Yes Yes No Yes
4. Participants and investigators are kept ‘blind’ about treatment allocation Yes No No No
5. The treatment and control groups are similar at the start of the trial Yes Yes Yes Yes
6. The only difference between groups is the treatment under investigation Yes Yes Yes Can't say
 7. All relevant outcomes are measured in a standard, valid and reliable way Yes Yes Yes Yes
 8. What percentage of the individuals or clusters recruited into each treatment arm of the study dropped out before the study was completed? CG: 76% IG1: 69% IG2:72% CG:44.8% IG: 43.3% CG: 28.9% IG: 23.2% 44.2% in general, no available information by group
 9. All the participants are analysed in the groups to which they were randomly allocated (often referred to as intention-to-treat analysis) Yes Yes Yes, see ítem 12 Yes
10. Where the study is carried out at more than one site, results are comparable for all sites Does not apply Can't say Yes Can't say
11. How well was the study done to minimise bias? Acceptable Acceptable Acceptable Acceptable
12. Taking into account clinical considerations, your evaluation of the methodology used, and the statistical power of the study, are you certain that the overall effect is due to the study intervention? Yes Yes  Only on those individuals followed at least 1 month Not clear, since a higher percentage of younger participants were lost

CG, control group; IG, intervention group; NRT, nicotine replacement treatment; SIGN, Scottish Intercollegiate Guidelines Network.