title: Final follow-up of the Multicentre Aneurysm Screening Study (MASS) randomized trial of abdominal aortic aneurysm screening.
abstract: BACKGROUND
  The long-term effects of abdominal aortic aneurysm (AAA) screening were investigated in extended follow-up from the UK Multicentre Aneurysm Screening Study (MASS) randomized trial.
  
  
  METHODS
  A population-based sample of men aged 65-74 years were randomized individually to invitation to ultrasound screening (invited group) or to a control group not offered screening. Patients with an AAA (3·0 cm or larger) detected at screening underwent surveillance and were offered surgery after predefined criteria had been met. Cause-specific mortality data were analysed using Cox regression.
  
  
  RESULTS
  Some 67 770 men were enrolled in the study. Over 13 years, there were 224 AAA-related deaths in the invited group and 381 in the control group, a 42 (95 per cent confidence interval 31 to 51) per cent reduction. There was no evidence of effect on other causes of death, but there was an overall reduction in all-cause mortality of 3 (1 to 5) per cent. The degree of benefit seen in earlier years of follow-up was slightly diminished by the occurrence of AAA ruptures in those with an aorta originally screened normal. About half of these ruptures had a baseline aortic diameter in the range 2·5-2·9 cm. It was estimated that 216 men need to be invited to screening to save one death over the next 13 years.
  
  
  CONCLUSIONS
  Screening resulted in a reduction in all-cause mortality, and the benefit in AAA-related mortality continued to accumulate throughout follow-up.
  
  
  BACKGROUND
  ISRCTN37381646 (http://www.controlled-trials.com).
authors.affiliation: Department of Public Health and Primary Care, University of Cambridge, UK. sgt27@medschl.cam.ac.uk
authors.forename: S G
authors.initials: SG
authors.lastname: Thompson
authors.forename: H A
authors.initials: HA
authors.lastname: Ashton
authors.forename: L
authors.initials: L
authors.lastname: Gao
authors.forename: M J
authors.initials: MJ
authors.lastname: Buxton
authors.forename: R A P
authors.initials: RA
authors.lastname: Scott
mesh_terms: D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000175:diagnosis / Q000401:mortality* / Q000601:surgery; D001019:Aortic Rupture / Q000175:diagnosis / Q000401:mortality* / Q000601:surgery; D002423:Cause of Death; D042241:Early Diagnosis; D005500:Follow-Up Studies; D006801:Humans; D008297:Male