| 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 |
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