Screening for Abdominal Aortic Aneurysm

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Screening for Abdominal Aortic Aneurysm

• Frank A. Lederle, MD

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Early History of AAA Screening

• Schilling (began in 1964!) 26 of 873 (3.1)
  white men aged 55-64 had AAA (? 3.6 cm) by abd
  palpation lateral x-rays (Circulation 1966 , J
  Chron Dis 1974)
• Cabellon 7 of 73 (9.5) vascular pts aged 43-79
  had AAA by abd palpation US (Am J Surg, Nov
  83)
• Also Nov 83, Twomey at VSSBGI meeting
  US screening ? 9 AAA in 84 English men
  gt age 50
• Followed by more 1-site (later) pop-based
  series (most in UK)

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Typical example of crude early studies
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Criteria for Screening(adapted from Frame
Carlson, 1975)

1. Detection treatment of the disease before
   symptoms appear must result in lower
   morbidity/mortality than treatment after symptoms
   appear (effective treatment - RCTs)
2. Screening must be acceptable to patients and
   cost-effective (simple test, common disease)

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Screening why not just do it?

• We believe there is an ethical difference between
  everyday medical practice and screening. If a
  patient asks a medical practitioner for help, the
  doctor does the best he can. He is not
  responsible for defects in medical knowledge. If,
  however, the practitioner initiates screening
  procedures he is in a very different situation.
  He should, in our view, have conclusive evidence
  that screening can alter the natural history of
  disease in a significant proportion of those
  screened.
• Cochrane Holland, Br Med Bull 197127(1)3-8

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Randomized Trials of AAA Screening

• Four trials in men - aged 65 to 73-83
• Randomized a population list,
  invited half to screening
• Screening was by ultrasound
• 60-80 attended
• 4-8 of these had AAA (? 3.0 cm)
• 1 outcome AAA-related death by intent to treat
• Non-emergency AAA repair ? 2-3 fold in invited
  group

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Meta-analysis of odds ratios of all cause long
term mortality in men
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??
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Re-Screening?

• ADAM 2622 pts (50-79 yo) lt 3.0 cm re-screened
  after 4 yrs
• (Lederle, Arch Intern Med 20001601117)
• Gloucestershire 223 men (65 yo) lt 2.6 cm, after
  5 12 yrs (Crow, Br J Surg 200188941)
• Chichester 649 men (65 yo) lt 3.0 cm, q 2 yr up
  to 10 yrs
• (Scott, EJVES 200121535)
• All found low yield, small AAA, concluded not
  worthwhile
• Chichester 95 of ruptures in district were in
  men gt 65 yo
• Conclusion One-time screen at age 65
• .

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MASS 10 yr BMJ 6/27/09
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After the Screening Test

• Inform patient of negative test result
• more reassuring than no news is good news
• Large AAA - consider elective repair
• AAA lt5.5cm ultrasound surveillance (ADAM, UKSAT)
  
• AAA ? 4.0 cm every 6 months (ADAM)
• AAA lt 4.0 cm every 2-3 years
• (Grimshaw, EJ VS 19948741 Santilli, JVS
  200235666)
• Quit smoking (AAA enlargement ? in quitters)
• (MacSweeney, Lancet 1994344651)

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Cost-Effectiveness of AAA Screening

• MASS study 1st report ? 45,000 per YOLS
• At 10 yr report, ? 15,000 per YOLS
• Viborg 10 ? 157 per YOLS (US 28)
• 5 of 6 earlier CEAs (not based on trials)
  concluded screening was cost-effective
• Elective repair lt 20,000 in European trials, but
  gt 47,000 in USA (Lee, JVS 200439491)
• No recent cost-effectiveness analysis for USA
• USPSTF EPC estimates lt 20,000 per QALY

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• Recommended one-time ultrasound screening for AAA
  in men aged 65-75 who ever smoked (B)
• No recommendation for men who never smoked (C)
• Recommend against routine AAA screening in women
  (D)

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SAAAVE Act brings (some) Medicare coverage

• Medicare (covers Americans over age 65) does not
  include preventive services, so each requires an
  act of Congress
• After USPSTF report, Congress added a Medicare
  benefit for ultrasound AAA screening at the
  Welcome to Medicare visit
• Covers male ever-smokers anyone with family
  history of AAA
• Problem the Welcome to Medicare visit is only
  for those aged 65-66!

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Will the benefits seen in the AAA screening
trials be achieved in U.S. practice?

• The AAA screening trials had strict eligibility
  criteria
• In MASS, the key trial, AAA repaired only when
  5.5 cm (per UKSAT ADAM)
• If AAA screening and/or repair is employed much
  more widely than in the trials, ratio of benefit
  to harm cost will likely decrease
• This is what seems to be happening in the U.S.A.

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SVS/AAVS/SVMB Consensus Statement

• Proposed criteria for AAA screening eligibility
  much broader than USPSTF or RCTs, including
• Men aged 60-85
• Women aged 60-85 with CV risk factors
• Anyone gt age 50 with a family history of AAA

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• In recently published U.S. ultrasound screening
  programs
• Most screenees were women
• The yield of AAA was (therefore) low

Program Number Screened Proportion of women Prevalence of AAA 3.0 cm Prevalence of AAA 3.0 cm
Men Women
AVA 7,841 60 4.5 0.85
DARE to CARE 12,055 59 3.2 0.5
Life Line 07 17,540 57 3.9 0.7
PROMIS 979 31 4.0 0.0
Many U.S. screening programs may be much less
cost-effective than the RCTs
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Repair of small AAA in U.S. - Practice

• gt59 of EVR at Cleveland Clinic (1996-2002) was
  on AAA lt 5.5 cm (Ouriel, J Vasc Surg
  2003371206)
• 1/4 of AAA deaths in U.S. result from elective
  repair
• 5000 deaths/yr from AAA rupture (CDC Wonder)
• 45,000 intact AAA repairs/year with 3 mortality
  ? 1400 deaths (McPhee, JVS
  07)
• gt1/3 of AAA deaths are w/o mention of rupture
  (CDC)
• Screening in USA could lead to repair of many
  small AAA, resulting in more deaths

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• Used large Life Line dataset to identify pts w
  AAA gt3 cm by generating score that expands the
  target population for screening beyond USPSTF
• Additional AAA mostly in women and men lt 65
• Rupture rare before 65 (though 3 cm AAA is not)
• The only RCT in women showed no benefit
• Dx of small AAA would ?( cost, repairs,
  deaths?), but no evidence for ? benefit
• SVS now lobbying Congress to pressure USPSTF

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Conclusion

• Many in U.S. who should be screened arent
• Many in U.S. who shouldnt be screened are
• If screening in U.S. leads to a large increase in
  elective repair in patients whose AAA would never
  have ruptured, the benefit seen in the RCTs may
  be lost