| Study | Assembly of Comparable Groups: Randomization/Allocation Concealment | Maintenance of Comparable Groups | Outcomes Assessment: Validity of Method, Masking | Attendance, Compliance, Contamination, Crossovers | Analysis, Exclusions, and External Validity | Study Quality |
|---|---|---|---|---|---|---|
| Northwest London Mass Radiography Service35,36 | Cluster randomized by random number; examiners not clearly blind; comparable in age structure and smoking habits; no apparent occupational exposures | 99% followup | Cause of death determined from hospital records and General Register's office; blinding not described | Intervention: 63% Control: 63% Cross-over: NR |
Intention-to-treat analysis; no reported exclusions; age and smoking habits similar | Fair |
| Kaiser Permanente33,34 | Randomized by patient record numbers with concealed code; more chronic lung disease in intervention group (8.9% vs 7.5%) | Poor followup | Blind review of death | Intervention: 60% underwent MHC (mean, 6.8 exams) Cross-over: 64% of controls had MHC (mean, 2.8 exams) |
Very low-risk population | Poor |
| Memorial Sloan-Kettering37,63-67 | Computer-generated randomization (not described); all cause mortality similar | Formal protocol/algorithm for followup; 55 lost to followup | All deaths reviewed by statisticians, clinicians, and pathologists blind to study group | Dual screen: 63.2% CXR: 65.2% |
Intention-to-treat analysis; only exclusion was prior lung cancer | Fair |
| Johns Hopkins38,68-72 | Computer generated randomization (not described); allocation concealment unclear; fairly comparable when evaluated by age, smoking history, non-tobacco carcinogen exposure | Formal algorithm for followup; 1.3% lost to followup | All deaths reviewed by statisticians, clinicians, and pathologists blind to study group | Uncertain; 19% withdrew from active screening | Intention-to-treat analysis; formal protocol for evaluation; only exclusion was prior lung cancer | Fair |
| Mayo Lung Project39,74-76,80 | Randomization method not described; allocation concealment unclear; similar distribution age, smoking exposure to non-tobacco carcinogens, and pulmonary disease | Adequate; good followup of all participants in both groups | All deaths reviewed by statisticians, clinicians, and pathologists blind to study group; National Death Index used for latest followup | Intervention: 75% Cross-over: 73% of controls had CXR within last 2 yrs of study |
Intention-to-treat analysis; formal protocol for evaluation; Mayo Clinic population with life expectancy estimates of 5 yrs | Fair |
| Czech40,84,85 | Randomization stratified by age, smoking history, socioeconomic status, residence, occupational exposure; allocation concealment unclear; no differences observed in these characteristics; all cause mortality, smoking-related deaths higher in intervention group | Not well reported | Cause of death ascertained from death certificates; autopsy in 1/3 of patients; blind review not described | Intervention: 92.5% Cross-over: rare |
Significantly higher all-cause mortality in screened group, suggesting bias in randomization | Poor |
| Wilde47 | Nonrandomized; similar community distribution of smoking habits and economic structure; similar all-cause mortality rates; population age not described | Adequate description; greater number dropouts in control group | Blinding not described; nonsystematic ascertainment of cause of death | NR | Intention-to-treat analysis; no reported exclusions; mortality rates not adjusted for age | Poor |
Notes: CXR, chest x-ray; MHC, multiphasic health checkups; NR, not reported.