Study designs of evaluations included in the review
Randomised controlled trials (RCTs) with at least 25 patients per treatment arm and a minimum follow-up period of 6 months were eligible for inclusion in the review. Observational studies were also included but these were not the main focus of the review. In the included RCTs, the duration of follow-up ranged from 9 to 36 months.
Specific interventions included in the review
Studies that evaluated the provision of spirometry test results alone or in conjunction with another intervention for smoking cessation were eligible for inclusion. In all but one of the included studies, smoking cessation counselling was provided to both treatment groups. Similarly, in all but one of the included studies, cointerventions that had been proven to improve smoking cessation rates were used for experimental groups. The majority of studies provided relevant training to health care providers. None of the studies used a hand-held spirometer.
Participants included in the review
Studies of current smokers were eligible for inclusion, regardless of respiratory symptoms or spirometry results. Where reported, the participants in the included studies had a mean age of 42 years (range: 16 to 75) and 90% were male. In none of the studies was participant selection based on motivation to quit. The participants included out-patients, workers and volunteers; in some studies the participants were at high risk (based on cardiopulmonary status or previous exposure to asbestos).
Outcomes assessed in the review
Studies that assessed smoking cessation rates were eligible for inclusion. The primary review outcome was long-term sustained abstinence, measured at least 6 months after the start of the intervention; abstinence could be measured biochemically by cotinine or expired carbon monoxide levels, or based on self-report (biochemical validation was preferred). The secondary review outcomes were patient self-reported and point prevalence abstinence, attempts at quitting and changes in lung function.
How were decisions on the relevance of primary studies made?
The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.