4. Response, adherence and contamination rates.

	Response rates to recruitment	Adherence to screening	Contamination
Aberle 2011	Not available	Overall adherence to all 3 screening rounds: 95% of participants completed LDCT scan, 93% in the control group completed CXR	Not available
Becker 2020	292,440 people received questionnaires 95,797 people responded 4913 people met eligibility criteria 4052 people were enrolled and randomised to the trial (1% of those who received a questionnaire, and 4% of respondents)	Baseline: almost 100% completed LDCT scan. 1‐year: 95% completed LDCT scan. 2‐year: 93% completed LDCT scan. 3‐year: 93% completed LDCT scan. 4‐year: 94% completed LDCT scan.	10 years postrandomisation: 264 participants in the control arm had received a CT.
Blanchon 2007	830 eligible people were approached 765 people consented to be randomised (92% of eligible people)	Baseline: 86% participants completed LDCT scan, 75% in control arm completed CXR.	At baseline: 6 participants in the control arm inadvertently received a LDCT.
De Koning 2020	606,409 people received the first questionnaire 150,920 responded to the questionnaire 30,959 people were eligible and invited to participate 15,822 people completed second questionnaire and were included and randomised (3% of people who received the first questionnaire and 51% of eligible respondents)	Baseline: 95% of participants completed LDCT scan 1 year: 97% of participants completed LDCT scan 3 years: 95% completed LDCT scan 5.5 years: 78% of participants completed LDCT scan	At 2 years: 3.6% of participants in the control arm had received CT for any reason
Field 2021	247,354 people invited to participate in study 75,958 responded positively to invitations 8729 of respondents assessed as high risk 5967 responded to second questionnaire 4868 invited to recruitment centre 4152 attended recruitment centre 4061 consented to participation  4055 randomised to trial (2% of those invited and 46% of high‐risk respondents)	Baseline: 98% of participants completed LDCT scan	Not available
Gohagan 2005	653,417 people mailed information packages 12,270 people contacted screening centre and underwent eligibility assessment 4828 people eligible for trial 3409 people were randomised, however 91 participants subsequently found to be ineligible  3318 participants randomised and included in analysis (1% of people who received mail packages and 27% who were screened for eligibility)	Baseline: 95% of participants completed LDCT scan, 93% of the control group completed CXR 1‐year: 86% of participants completed LDCT scan, 80% of the control group completed CXR	Contamination assessed by random sample of participants At baseline: 5% of respondents in the intervention arm had received a CXR for medical or screening purposes. 0.9% of respondents in the control arm had received a CT for medical or screening purposes. At 1 year: 10% of participants in the intervention arm had received a CXR for medical or screening purposes and 1.3% of respondents in the control arm had received a CT for medical or screening purposes.
Infante 2015	Not available	Not available	3 years post‐randomisation: intervention arm (74 extra CT scan, 233 extra CXRs) control arm (extra 68 CTs, 209 extra CXRs) Did not specify if for screening purposes, only outside protocol
LaRocca 2002	3418 people completed screening questionnaires 904 participants completed pre‐screening baseline CXR 871 participants randomised to trial (25% of people who completed screening questionnaire)	Not available	Not available
Paci 2017	71232 people sent letters 17,055 people responded to letters 3206 people were eligible and randomised (5% of people who received letters and 19% of respondents)	Baseline: 87% completed LDCT scan 1 year: 85% completed LDCT scan 2 years: 82% completed scan 3 years: 80% completed scan	Not available
Pastorino 2012	Not available	Baseline: 97% of annual group completed scan, 97% of biennial group completed scan 1 year: 97% of the annual group and 97% of the biennial group completed the scan 2 years: 98% of the annual group and 95% of the biennial group completed the scan 3 years: 97% of the annual group and 97% of the biennial group completed the scan 4 years: 96% of the annual group and 92% of the biennial group completed the scan 5 years: 79% of the annual group and 98% of the biennial group completed the scan 6 years: 54% of the annual group and 77% of the biennial group completed the scan	10 years post‐randomisation: 21 of 1723 participants in the control arm had received a LDCT
Wille 2016	5861 people assessed for eligibility 4104 people randomised to the trial (70% of people assessed)	Not available	After 5 years post‐randomisation: 0 cases of contamination in the intervention arm; 3 cases in the control arm

CT: computed tomography; CXR: chest x‐ray; LDCT: low‐dose computed tomography