Evidence for AAA Screening and Cost Effectiveness

Question 1

Pilot Study:

Answer 1

Chichester, 1995

Question 2

Methods of Pilot Study:

Answer 2

16,000 patients males and females aged 65-80 years old
RCT:
1) Control
2) Screening

Question 3

Outcomes of Pilot Study:

Answer 3

Screening REDUCED rupture rates by 55% in males but negligibly reduced rupture rates in females.
Provided grounds for a bigger screening trial in males only.

Question 4

Key trial for AAA Screening:

Answer 4

MASS-Multicentre Aneurysm Screening Study

Question 5

Methods of MASS:

Answer 5

RCT spanning 1997-1999
Had a 13 year follow up which provides good evidence of outcomes
68,000 males aged 65-74 identified from GP lists
Randomised to either control or screening
Cut offs:
<3.0cm = normal
3.0-4.4cm = annual screening
4.5-5.4cm = 3 monthly screening
>5.5cm or >1cm growth per year = surgical repair

Question 6

Outcomes of MASS at 13 year follow up:

Answer 6

Showed prevalence of AAA was 4.63%
Screened group had HALF the number of emergency procedures but TWICE the number of elective repairs (better because emergency carries more risk than elective)
Screening reduced AAA-related death by 42%
59 men in the screened group who had a normal first scan suffered AAA rupture-occurred mostly at ~8 years so raises potential for a second follow up scan (in line with findings of RESCAN)

Question 7

NHS Introduction of Screening Programme:

Answer 7

2009-Evaluated at 5 years by JACOMELLI 2016

Question 8

Outcome of Jacomelli 2016 Evaluation:

Answer 8

80% of invited males attended their scan-uptake lower in lower socioeconomic areas
98.7% <0.3cm = incidence of AAA only 1.3% which is A LOT lower than the MASS trial and UKSAT showed
Showed there is a spike in AAA incidence at 3.0cm-because people with 2.8/9cm were bumped up to 3.0cm to ensure they were scanned-should these people have a later follow up?

Question 9

Cost Effectiveness of Screening:

Answer 9

MASS performed a Sub-analysis of Screening costs based on the financial year 2000-2001 (Likely to be different now but similar principles)

Question 10

Outcomes of MASS Cost-effectivness Sub-Analysis:

Answer 10

At 4 years, screening saved 47 lives but at an additional cost of £2.2 million
Mean cost of screening per person = £63
More money spent on elective surgery but significantly less of emergency which carries more risk
Was not below NICE QALY threshold of

Question 11

Problems with Cost-effectiveness analysis:

Answer 11

The cost-effectiveness analysis was based on an AAA prevalence of 4.63%, whereas the actual prevalence as shown by Jacomelli is only 1.3%-so it is likely not to be cost effective in real practice

Question 12

Who is it not cost-effective to screen?

Answer 12

The population prevalence of AAA is 3.0x higher in males than females and as shown in the chichester pilot study screening females made negligible difference to rupture rates

Question 13

Should Consideration for Screening be given to subgroups?

Answer 13

SMOKING: ever smoking increases risk of AAA 5x so perhaps ever-smoking should warrant screening. Plus, smoking take up in females was delayed compared to males, so whilst screening was not effective in the 90’s, it may be now.
FAMILY HISTORY: larsson et al showed family history of ruptured AAA increases odds 1.9x. So could be cost effective to screen those with family history
ETHNICITY: Leicester screening programme showed asian prevalence of AAA is much lower, so might not be cost effective to screen certain ethnicities.