ADAM.

Methods	Study design: intention to treat Method of randomisation: equal probability of assignment to each of the two study groups using automated telephone/computer Concealment of allocation: unblinded
Participants	Country: United States Number: 1136 Age: 50 to 79 years Sex: men (n = 1126) and women (n = 10) Inclusion criteria: small (4.0 cm to 5.5 cm) non‐tender asymptomatic AAAs considered fit for immediate surgery. Patients who were considered unfit for immediate surgery, had symptoms associated the aneurysm, were unable to attend the follow‐up visit, or were unable to give informed consent were excluded. Patients who received a revascularization procedure within 3 months of enrolment, who had a myocardial infarction within 6 months of enrolment, or who were expected to survive less than 5 years because of invasive cancer or other life‐threatening disease were also excluded.
Interventions	Treatment: surgery, n = 569 of whom 527 had immediate aneurysm repair; 42 had no elective operation due to death, refusal, etc. Surveillance, n = 567 of whom 349 had aneurysm repair when they met the criteria listed below (in 9%, the procedures were performed despite an AAA that did not meet the repair criteria listed below). Participants assigned to the immediate‐surgery group received standard open repair within 6 weeks after randomisation, while participants assigned to selective surveillance were followed without repair at similar regular intervals (at minimum once every 6 months), and surgery was performed within 6 weeks if: a) the aneurysm reached 5.5 cm; or b) the aneurysm enlarged by a minimum of 0.7 cm in 6 months or 1.0 cm in 1 year; or c) the aneurysm became symptomatic.
Outcomes	Primary: survival during mean follow‐up (range 3.5 to 8.0 years, mean 4.9 years) (30‐day surgical mortality) Secondary: healthcare costs
Notes	Supported by the Cooperative Studies Program of the Department of Veterans Affairs Office of Research and Development, Washington, DC, USA
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	The method of randomisation was of equal probability of assignment to each of the two study groups using automated telephone/computer.
Allocation concealment (selection bias)	Unclear risk	Concealment of allocation: unblinded
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Cannot blind participants
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Unlikely given the study outcome (mortality) and low lost‐to‐follow‐up rate. Vital status was assessed using the same methodology for both participants in the immediate‐repair group and participants in the routine ultrasound surveillance group‐‐in case misclassification occurred this would have been non‐differential and its impact on the study results would be limited.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Unlikely given the study outcome (mortality) and low lost‐to‐follow‐up rate
Selective reporting (reporting bias)	Low risk	Authors published findings on all the study outcomes including the study outcome of this review.
Other bias	Low risk	We did not identify other possible risk of bias.