Comparison 9. Sub‐group: risk of bias in the studies.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Patient asked to set a quit date	8	4332	Odds Ratio (IV, Random, 95% CI)	4.97 [1.85, 13.30]
1.1 Up to and including 2 domains	7	4129	Odds Ratio (IV, Random, 95% CI)	5.67 [1.96, 16.42]
1.2 From 3 to 5 domains	1	203	Odds Ratio (IV, Random, 95% CI)	1.68 [0.31, 9.00]
2 Patient asked to make a follow‐up appointment	7	3114	Odds Ratio (IV, Random, 95% CI)	3.34 [1.19, 9.34]
2.1 Up to and including 2 domains	6	2911	Odds Ratio (IV, Random, 95% CI)	3.79 [1.14, 12.55]
2.2 From 3 to 5 domains	1	203	Odds Ratio (IV, Random, 95% CI)	1.68 [0.69, 4.06]
3 Number of smokers counselled	14	8531	Odds Ratio (IV, Random, 95% CI)	2.28 [1.41, 3.67]
3.1 Up to and including 2 domains	11	7804	Odds Ratio (IV, Random, 95% CI)	2.32 [1.34, 4.02]
3.2 From 3 to 5 domains	2	435	Odds Ratio (IV, Random, 95% CI)	1.64 [0.87, 3.10]
3.3 From 6 to 8 domains	1	292	Odds Ratio (IV, Random, 95% CI)	3.42 [1.61, 7.28]
4 Number of smokers receiving self‐help material	9	5157	Odds Ratio (IV, Random, 95% CI)	3.26 [1.57, 6.77]
4.1 Up to and including 2 domains	8	4722	Odds Ratio (IV, Random, 95% CI)	4.08 [1.75, 9.55]
4.2 From 3 to 5 domains	2	435	Odds Ratio (IV, Random, 95% CI)	1.48 [0.64, 3.42]
5 Number of smokers receiving nicotine gum/replacement therapy	9	5073	Odds Ratio (IV, Random, 95% CI)	1.57 [0.72, 3.41]
5.1 Up to and including 2 domains	6	4146	Odds Ratio (IV, Random, 95% CI)	1.44 [0.54, 3.81]
5.2 From 3 to 5 domains	2	435	Odds Ratio (IV, Random, 95% CI)	1.47 [0.57, 3.76]
5.3 From 6 to 8 domains	1	492	Odds Ratio (IV, Random, 95% CI)	3.53 [0.95, 13.09]