Parkes 2008.

Study characteristics
Methods	Design: Randomized controlled trial Setting: 5 general practices in Hertfordshire, UK Recruitment: Identified potentially eligible participants by searching computerized patient records from the practices. A letter of invitation was sent to the identified patients. 2 weeks later,  those who had not already responded were telephoned and offered an invitation to participate. Those who could not be contacted by telephone were sent a second letter
Participants	561 adults who smoked (> 35 years). av.age 53, 46% M, 17 cpd
Interventions	Intervention: Participant performed spirometry then was given their results verbally in the form of “lung age” with a graphic display. Within 4 weeks of data collection the research doctor sent all participants an individualized letter. Written results were given to the intervention group as “lung age.” Control: Participants were not told their spirometry results, but informed that they would be invited for a second test after 12 months to “see if there had been any change in lung function.” Within 4 weeks of data collection the research doctor sent all participants an individualized letter. Written results were given to the control group as simple FEV1 (liters per second) with no further explanation
Outcomes	24‐hour PPA at 12m Validation: Salivary cotinine < 14.2 ng/ml
Funding Source	Funding: Leading practice through research award from the Health Foundation
Author's declarations of interest	Authors declared that they had no competing interest
Notes	Strategy: Spirometry (Lung age monitoring) Level: Patient Comparison type: Single component vs. standard care
Risk of bias
Bias	Authors' judgement	Support for judgement
Sequence Generation	Low risk	Clerk prepared 600 sequentially‐numbered opaque sealed envelopes, each containing a card with allocation group determined by computer‐generated random number
Allocation concealment	Low risk	Opaque sequentially‐numbered sealed envelopes
Blinding of outcome assessors All outcomes	Low risk	Smoking abstinence was biochemically validated
Incomplete outcome data All outcomes	Low risk	The overall loss to follow‐up was 11.2% (n = 63/561); 11.1% (n = 31/280) in the intervention group and 11.4% (n = 32/281) in the control group were lost to follow‐up at 12 months