Screening for Abdominal Aortic Aneurysm

84 Pages·2013·3.11 MB·English

by  Sverker Svensjö

Digital Comprehensive Summaries of Uppsala Dissertations
from the Faculty of Medicine 903
Screening for Abdominal
Aortic Aneurysm
SVERKER SVENSJÖ
ACTA
UNIVERSITATIS
ISSN 1651-6206
UPSALIENSIS
ISBN 978-91-554-8668-6
UPPSALA
urn:nbn:se:uu:diva-198677
2013
Dissertation presented at Uppsala University to be publicly examined in Föreläsningssalen,
Falu Lasarett, Entré 6:C 01, Söderbaums väg 8, Falun, Friday, June 7, 2013 at 13:15 for the
degree of Doctor of Philosophy (Faculty of Medicine). The examination will be conducted
in English.
Abstract
Svensjö, S. 2013. Screening for Abdominal Aortic Aneurysm. Acta Universitatis Upsaliensis.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine
903. 82 pp. Uppsala. ISBN 978-91-554-8668-6.
Randomised controlled trials have demonstrated that mortality from Abdominal Aortic
Aneurysm (AAA) can be cost-effectively reduced by ultrasound-screening of men. Evidence
for screening women is insufficient. Reports of falling AAA incidence are emerging.
In an effort to study screening for AAA in a contemporary setting, two cross-sectional multi-
centre population-based studies of one-time screening of 65-year-old men, and 70-year-old
women in Middle Sweden were undertaken. Cost-efficiency of one-time screening of 65-year-
old men was evaluated in a decision-analysis model. Five-year outcomes in men invited to
screening at age 65 and age 70, were studied in a longitudinal cohort study.
A lower than expected (1.7%) prevalence of AAA in 65-year-old men was found, as well as
a very low (0.4%) prevalence in 70-year-old women. Smoking was the dominating risk factor
associated with AAA, but the association was stronger in women. The main cause of reduced
contemporary prevalence was falling smoking rates in the population since 30 years.
One-time screening of 65-year-old men was found to be cost-effective and deliver significant
clinical impact. The cost per quality adjusted life-year gained, at 13-years follow-up, was
€14706, which was below the recommended UK NICE threshold of €25000. 15 lives were saved
by inviting 10000 to screening. Prevalence of AAA and the rate of incidental detection of AAAs
in the population were important factors affecting cost-efficiency.
New AAAs developed after 5 years in men screened normal at age 65, predominantly in men
with sub-aneurysmal aortas (25-29mm) at 65, and smokers. The 5-year rate of AAA repair was
high among men with screening detected AAAs, as was non-AAA related mortality. Ruptures
were only documented among non-attenders.
Conclusions: A lower than expected prevalence of AAA among 65-year-old men, an
unchanged repair rate, and improved longevity of the elderly population was found. Although
one-time screening for AAA was still cost-effective within a contemporary context, several
issues need to be addressed; the threshold diameter for follow-up, the current rate of
opportunistic detection of AAA in the population, re-screening of the entire population at a
higher age, and targeted screening of smokers. Screening 70-year-old women who do not smoke
is likely to be futile, thus ruling out population screening of women for AAA.
Sverker Svensjö, Uppsala University, Department of Surgical Sciences, Akademiska sjukhuset,
SE-751 85 Uppsala, Sweden.
© Sverker Svensjö 2013
ISSN 1651-6206
ISBN 978-91-554-8668-6
urn:nbn:se:uu:diva-198677 (http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-198677)
To Lena, Joel, Emil and Anton

List of Papers
This thesis is based on the following papers, which are referred to in the text
by their Roman numerals.

I Svensjö, S, Björck, M, Gürtelschmid, M, Djavani-Gidlund, K,
Hellberg, A, Wanhainen A. Low prevalence of abdominal aortic
aneurysm among 65-year-old Swedish men indicates a change
in the epidemiology of the disease.
Circulation, 2011;124(10):1118-1123

II Svensjö, S, Björck, M, Wanhainen A. Current prevalence of ab-
dominal aortic aneurysm in 70-year-old women.
Br J Surg, 2013;100(3):367-372

III Svensjö, S, Mani, K, Björck, M, Lundkvist, J, Wanhainen A.
Screening for Abdominal Aortic Aneurysm in 65-year-old Men
remains Cost-effective with Contemporary Epidemiology and
Management.
Submitted Manuscript

IV Svensjö, S, Björck, M, Wanhainen A. Five-year outcomes in
men screened for abdominal aortic aneurysm at 65 years of age,
a population-based cohort study
Manuscript

Reprints were made with permission from the respective publishers.

Contents
Introduction ................................................................................................... 11
Abdominal Aortic Aneurysm ................................................................... 11
Epidemiology ........................................................................................... 13
Vascular ultrasound, arterial duplex scanning ......................................... 15
Screening .................................................................................................. 16
Areas lacking information ........................................................................ 18
Changing epidemiology and AAA management ................................. 18
Screening Women for AAA ................................................................ 19
Development of AAAs after a normal screening scan ........................ 19
Aims .............................................................................................................. 20
Subjects, Material, and Methods ................................................................... 21
Subjects, methodology, and study design ................................................ 21
Study I .................................................................................................. 21
Study II ................................................................................................ 22
Study III ............................................................................................... 23
Study IV ............................................................................................... 27
Ultrasound ................................................................................................ 27
Definition of an AAA .......................................................................... 28
Definition of a sub-aneurysmal aorta................................................... 28
Surveillance intervals ........................................................................... 28
Threshold for AAA repair ................................................................... 28
Statistics and Ethics .................................................................................. 29
Etiological Fraction ............................................................................. 29
Results ........................................................................................................... 31
Study I ...................................................................................................... 31
Study II ..................................................................................................... 32
Study III ................................................................................................... 34
Study IV ................................................................................................... 37
General Discussion ....................................................................................... 41
Changing Epidemiology ........................................................................... 41
Prevalence and risk factors .................................................................. 41
Rate of AAA repair .............................................................................. 44
Implications for screening (effect and cost-effectiveness) .................. 46
Screening Women for AAA ..................................................................... 51
Outcomes in men screened for AAA ....................................................... 53
Non-attenders ....................................................................................... 53
Men screened <25mm at age 65 .......................................................... 54
Sub-aneurysmal aortas and surveillance .............................................. 54
Men with AAA .................................................................................... 58
Future perspective .................................................................................... 59
Conclusions ................................................................................................... 60
Summary in Swedish .................................................................................... 62
Acknowledgements ....................................................................................... 65
References ..................................................................................................... 68
Abbreviations
AAA Abdominal Aortic Aneurysm
CT Computerised Tomography
EVAR Endovascular Aneurysm Repair
HR Hazard Ratio
LELE Leading Edge to Leading Edge
MRI Magnetic Resonance Imaging
O.R. Odds Ratio
ODR Opportunistic Detection and Repair Rate of AAA
OR Open Repair
QALY Quality Adjusted Life-year
RCT Randomised Controlled Trial
Swedvasc The Swedish Vascular Registry
US Ultrasound/Ultrasonography