Table 1

Design of screening studies comparing different frequencies of chest radiographic screening

Study and year commencedSubjectsInterventionControlScreening durationTotal follow up*
*Follow up period includes period of active screening and post screening follow up. The maximum follow up is described; for some studies this varied as subjects were enrolled at different stages.
Erfurt County (1972)3Men aged 40–65 years. Smokers and non-smokers6 monthly chest radiographsChest radiographs every 1–2 years.6 years6 years
North London study (1960)14Men aged 40+ years. Smokers and non-smokers from 119 work sites (mainly factories)6 monthly chest radiographsChest radiograph at baseline and at the end of 3 years3 years3 years
Czech study (1976)16Men aged 40– 64 years. Current heavy smokers.6 monthly chest radiography and sputum cytology for the first 3 years followed by annual chest radiograph for 3 yearsChest radiograph at baseline and chest radiograph and sputum cytology after 3 years followed by annual chest radiographs for 3 years6 yearsInitially 6 years, later extended to 15 years
Mayo Lung Project (1971)4Men attending the Mayo Clinic aged more than 45 years. Heavy smokers4 monthly chest radiography and sputum cytologyAdvised at the start of the study to have an annual chest radiograph and sputum cytology test6 yearsInitially 11 years, later extended to 24 years.
Kaiser Permanente study (1964)18Men and women aged 35–54 years. Smokers and non-smokers. Members of Kaiser Permanente medical care programmeEncouraged to undergo an annual multiphasic health check up including an annual chest radiographSubjects not urged to undergo screening but could do so as part of their usual care if requested16 years16 years