Thirty-seven studies (of 38 comparisons) were included in the review, comprising 10 patient-level RCTs, two quasi-RCTs at patient level, two physician-level cluster RCTs, one physician-level quasi-RCTs, 13 practice-level cluster RCTs, and 10 before-and-after controlled studies (numbers of study designs differed slightly between the tables on descriptions of included studies). Duration of follow-up ranged from eight weeks to five years, where reported. The quality of the included studies was variable; many studies had a loss-to follow-up of more than 20%, few trials used blinding, and many of the cluster RCTs did not report adjustment for clustering.
Multi-component interventions (10 studies): Compared with control, multi-component interventions significantly increased the smoking abstinence rate (OR 2.19, 95% CI 1.71 to 2.79; I2=72%; seven studies). There was also evidence that multi-component had statistically significant effects on most components of the 5As.
Patient-level interventions (10 studies): Compared with control, adjuvant counselling significantly increased the smoking abstinence rate (OR 1.73, 95% CI 1.48 to 2.01; I2=37%; seven studies). There was also limited evidence that adjuvant counselling had some effects on components of the 5As but not on all components. The evidence for tailored print materials was limited (two studies), but appeared to indicate a statistically significant benefit on smoking abstinence. Sensitivity analyses showed that results remained significant for adjunct councelling for smoking abstinence, but results were no longer significant for tailored print materials for smoking abstinence.
Practitioner-level interventions (four studies): Compared with control, training did not significantly increase the smoking abstinence rate (two studies), or the Ask component of the 5As (one study). There was also mixed evidence for performance feedback on the 5As, but with some evidence of statistical heterogeneity (two studies).
Practice-level interventions (12 studies): There was mixed evidence for practice-level interventions on smoking abstinence and the 5As.
System-level interventions (two studies): There was limited evidence (one study) that provider incentives did not significantly increase smoking abstinence, and had mixed effects on certain aspects of the 5As.
Other results were provided in the review.