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A Sustained Mortality Benefit from Screening for Abdominal Aortic Aneurysm

Lois G. Kim, MSc; R. Alan P. Scott, MCh; Hilary A. Ashton, MSc; Simon G. Thompson, DSc, Multicentre Aneurysm Screening Study Group
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From the Institute of Public Health, Cambridge, United Kingdom, and St. Richard's Hospital, Chichester, United Kingdom.

Acknowledgment: The authors thank Professor Martin Buxton for comments on a previous version of this paper.

Grant Support: By the U.K. Medical Research Council. Ms. Kim receives a Raymond and Beverly Sackler Studentship Award.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Lois G. Kim, MSc, MRC Biostatistics Unit, Institute of Public Health, Robinson Way, Cambridge CB2 2SR, United Kingdom; e-mail, lois.kim@mrc-bsu.cam.ac.uk.

Current Author Addresses: Ms. Kim and Dr. Thompson: MRC Biostatistics Unit, Institute of Public Health, Robinson Way, Cambridge CB2 2SR, United Kingdom.

Mr. Scott and Ms. Ashton: Scott Research Unit, Chichester Medical Education Centre, St. Richard's Hospital, Spitalfield Lane, Chichester PO19 6SE, United Kingdom.

Author Contributions: Conception and design: R.A.P. Scott, H.A. Ashton.

Analysis and interpretation of the data: L.G. Kim, R.A.P. Scott, H.A. Ashton, S.G. Thompson.

Drafting of the article: L.G. Kim, R.A.P. Scott, H.A. Ashton.

Critical revision of the article for important intellectual content: L.G. Kim, R.A.P. Scott, S.G. Thompson.

Final approval of the article: L.G. Kim, R.A.P. Scott, H.A. Ashton, S.G. Thompson.

Statistical expertise: L.G. Kim, S.G. Thompson.

Obtaining of funding: R.A.P. Scott, S.G. Thompson.

Administrative, technical, or logistic support: R.A.P. Scott, H.A. Ashton.

Collection and assembly of data: R.A.P. Scott, H.A. Ashton.

Ann Intern Med. 2007;146(10):699-706. doi:10.7326/0003-4819-146-10-200705150-00003
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The details of the MASS protocol were described previously (2), but a brief summary is provided (Figure 1). Between 1997 and 1999, a population-based sample of 70 495 men age 65 to 74 years from 4 centers in the United Kingdom was identified by obtaining records for every man in this age range who was registered with a family physician (registered persons account for approximately 98% of the population). Persons who were ineligible for the trial (incorrect details, known AAA, previous AAA surgery, or terminal illness) were excluded before randomization. The remaining 67 770 men were randomly assigned to receive an invitation to ultrasonography for AAA or to not receive an invitation to ultrasonography. At screening, men with an aortic diameter of 3.0 cm or greater were defined as having an AAA and were subsequently invited for recall scans to monitor growth of the aneurysm. Men with an aortic diameter of 3.0 to 4.4 cm were rescreened every year, and those with an aortic diameter of 4.5 to 5.4 cm were rescreened every 3 months. Participants were considered for elective surgery when the aortic diameter reached 5.5 cm, aortic expansion was 1.0 cm or more in 1 year, or they experienced symptoms attributable to the aneurysm. Men with an aortic diameter less than 3.0 cm on the initial scan were not rescreened. Blood pressure was also measured; although family physicians were informed of these measurements, no further intervention was provided through the screening program. We obtained approval from local ethics committees at each center, and all patients who had screening provided signed informed consent.

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Figure 1.
Study flow diagram.

*Patients who should not have been included in the sample because they did not meet the inclusion criteria for the study (for example, because of age or because they were no longer registered at a participating practice). †Aneurysm was defined as an aortic diameter ≥30 mm.

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Figure 3.
Cost-effectiveness acceptability curve at 7-year follow-up for base-case analysis (abdominal aortic aneurysm death outcome, discounting costs and effects at 3% by using 2004–2005 prices).
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Figure 2.
Cumulative abdominal aortic aneurysm (AAA)–related mortality.
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Mortality Benefit from Screening for Abdominal Aortic Aneurysm
Posted on May 18, 2007
Hisato Takagi
Shizuoka Medical Center
Conflict of Interest: None Declared

The Multicentre Aneurysm Screening Study (MASS) (1), a randomized controlled trial (RCT) of abdominal aortic aneurysm (AAA) screening in men, provided that the hazard ratios were 0.53 (95% CI, 0.42 to 0.68) for AAA- related mortality and 0.96 (CI, 0.93 to 1.00) for all-cause death in the group invited for screening at a mean 7.1-year follow-up.

Our previous meta-analysis (2) of then available 4 RCTs of AAA screening in men (the Viborg Country trial [median follow-up, 9.6 years], the Western Australia trial [median, 3.6 years], the MASS [mean, 4.1 years] (3), and the Chichester trial [men] [mean for AAA-related mortality, 10 years; mean for all-cause mortality, 2.5 years]) demonstrated that an invitation to attend AAA screening reduced not all-cause (odds ratio [OR], 0.95; CI, 0.87 to 1.03) but AAA-related mortality (OR, 0.55; CI 0.37 to 0.83). According to a Cochrane review by Cosford and Leng (4) of 3 RCTs of AAA screening in men (the Western Australia trial [3.6 years], the MASS [4.1 years] (3), and the Chichester trial [men] [2.5 years]), there was a significant decrease in mortality from AAA in the screened group (OR, 0.60; CI, 0.47 to 0.78) but no significant difference in all-cause mortality between screened and unscreened groups (OR, 0.95; CI, 0.85 to 1.07).

Herein, we performed a meta-analysis of currently available RCTs of AAA screening in men including the 7.1-year follow-up MASS (1). Our comprehensive search identified 4 RCTs: the Viborg Country trial (9.6 years), the Western Australia trial (3.6 years), the MASS (7.1 years) (1), and the Chichester trial (men) (10 years for AAA-related mortality; 2.5 years for all- cause mortality). Although the pooled OR using a random-effects model showed a significant reduction in AAA-related mortality favoring screening (OR, 0.54; CI, 0.37 to 0.79), an invitation to attend screening was not associated with a significant reduction in all-cause mortality (OR, 0.94; CI, 0.88 to 1.02). There was significant between-study heterogeneity of results analyzed by means of standard ƒÔ2 tests (P = 0.047 for AAA-related mortality, P = 0.002 for all-cause mortality) but no evidence of significant publication bias assessed using an adjusted rank-correlation test.

Despite the results of the 7.1-year follow-up MASS (1), the present meta- analysis of all the currently available RCTs failed to show the all-cause mortality benefit of screening for AAA in men.

1. Kim LG, P Scott RA, Ashton HA, Thompson SG; Multicentre Aneurysm Screening Study Group. A sustained mortality benefit from screening for abdominal aortic aneurysm. Ann Intern Med. 2007;146:699-706. [PMID: 17502630]

2. Takagi H, Tanabashi T, Kawai N, Kato T, Umemoto T. Abdominal aortic aneurysm screening reduces mortality: meta-analyses of randomized, controlled trials. Eur J Vasc Endovasc Surg. 2007;33:132-3. [PMID: 17067830]

3. Ashton HA, Buxton MJ, Day NE, Kim LG, Marteau TM, Scott RA, et al. The Multicentre Aneurysm Screening Study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial. Lancet. 2002;360:1531-9. [PMID: 12443589]

4. Cosford P, Leng G. Screening for abdominal aortic aneurysm. Cochrane Database Syst Rev. 2007;(2):CD002945. [PMID: 17443519]

Conflict of Interest:

None declared

Mortality and aneusysm screening
Posted on June 1, 2007
Thomas E. Finucane
Johns Hopkins Bayview Medical Center
Conflict of Interest: None Declared

The Editors'summary of the article on abdominal aortic aneurysm screening by Kim and colleagues is dangerously misleading. It says, in part, "The 7-year follow-up report of a large randomized trial in the United Kingdom found that men age 65 to 74 years who were invited to have ultrasonography and surveillance for AAA had lower mortality rates than did those who were not invited (hazard ration, 0.053 [CI, 0.42 to 0.68])."

The actual mortality rate in the two groups was not different by conventional significance testing (hazard ratio, 0.96 [CI, 0.93 to 1.00], even though the invited group had fewer deaths from other cardiovascular causes, fewer deaths from cancer, and fewer deaths from all other causes. (The Editors are referring to the AAA-related mortality.)

Conflict of Interest:

None declared

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