Eur J Vasc Surg 8, 156-160 (1994)

An Abdominal Aortic Aneurysm Screening Programme for all Males over the Age of 50 Years

G. E. Morris, 1 C. S. ff. Hubbard 2 and C. R. G. Quick 3

1 Present address: Department of Surgery, The Ipswich Hospital, Ipswich, U.K., 2 Department of Radiology and 3 Department of Surgery, Hinchingbrooke Hospital, Huntingdon, U.K.

Previously published ultrasound screening programmes for abdominal aortic aneurysm (AAA) have concentrated on males in the 65 to 75 year age range, suggesting this as the most cost-effective cohort to target. In this unique study we have broadened the criteria for screening. General practitioners in one health district were approached to supply details of all males aged 50 years and over to be offered aortic ultrasound scanning. Over a period of 18 months, 4145 individuals were asked to attend and 3030 (73%) have attended. Attendance rates were: between 50 and 64 years, 73%; between 65 and 79 years, 75%;for 80 years and over, 64%--significantly less (p = 0.01-0.001) than the other two age bands. Aortic dilatation (diameter ~ 2.5 cm) was found in 6.3 % of the 50 to 64 year age group, 16.8 % of the 65 to 79 year age group, and 23.3 % of the 80 years and over age group. A n established aneurysm (>~4.6cm) was found in 0.3%--6 individuals (50-64 years), 2.5% (65-79 years) and 4.1% (>180 years). The results suggest that aortic screening may be worthwhile extending to a wider age band. By focusing follow-up, this should give greater value for younger men in terms of community productivity and allows for selective intervention in the elderly.

Key Words: Aortic aneurysm; Screening programme; Ultrasound scanning; Males over 50 years.

Introduction

The frequency of abdominal aortic aneurysm (AAA) is increasing in the western world, and there is an associated increased incidence of rupture. 1-s Elective repair of AAA carries an early mortality rate of less than 5%. 6'7 If rupture occurs, mortality may be 30% or less for those reaching hospital and undergoing resection, s'9 but the overall community mortality rate is as high as 85%, with the majority dying at home. 1° 12 Ultrasound scanning (US) has been shown to be an accurate and cheap method of diagnosis, significantly better than clinical examination. 13-16 The technique is reproducible, with single observer variation probably in the range of 3.5-7.5mm. 17"18 Pilot ultrasound screening programmes for AAA have been estab- lished in the U.K. 19-21 These have concentrated on males in the 65 to 75 year age range, postulating this to be the most cost-effective cohort to target. There is, however, little hard data on the workload generated by extending screening beyond this age range. In

* Presented at the 7th Annual Meeting of the European Society for Vascular Surgery, Barcelona, September 1993.

Please address all correspondence to: C. R. G. Quick, Department of Surgery, Hinchingbrooke Hospital, Hinchingbrooke Park, Huntingdon, Cambs., PE18 8NT, U.K.

younger men, successful detection and treatment of AAA obviously offers greater potential benefits than in the elderly, 22 but in older patients (including octo- genarians) AAA repair has also been shown to offer good survival rates and confers benefits in terms of longevity and quality of life. 23-25 For all age groups, quality of life is significantly better after elective as opposed to emergency repair, a6 The Chief Medical Officer is being pressed to approve a national screen- ing programme, and has indicated he will do so, if evidence of its benefit is forthcoming. 27

Patients and Methods

There are approximately 13 600 men over 50 years of age in the Huntingdon Health District. All these men, whether healthy or unfit, are required to be regis- tered with a general practitioner, thus making them all eligible for the study. We aim to examine a sample of approximately 8000 over a 3-year period. Individ- ual general practices have been invited to participate one at a time. Each practice has been visited by two of us (CRGQ and CH) and the principles of the screen- ing programme explained. The referring physicians

0950-821X/94/020156+05 $08.00/0 © 1994 W. B. Saunders Company Ltd.

AAA Screening for All Males over 50 Years 157

are then asked to generate lists of men of 50 years and over registered with them, and then to prescreen the notes to exclude individuals they would not regard as suitable for surgery if an aneurysm should be detected. Suggested criteria are: end-stage carci- noma, end-stage cardiac or respiratory disease, and senile or pre-senile dementia. Payment is offered for the extra clerical help needed for this. Potential par- ticipants are sent an invitation letter unde r their general practi t ioner 's (GP's) name, with an appoint- ment date and time, and given a te lephone number for enquiries or to change the appointment . Letters of invitation, results for GPs and individual recalls for rescreening are generated using a compute r pro- g ramme writ ten by one of us (CRGQ) and overseen by the project administrator.

Ul t rasound scanning, using a Siemens Sonoline II, is carried out in evening clinics held in the out- pat ient depar tmen t at Hinchingbrooke Hospital, U.K. Thirty appoin tments are made for each session and two sessions are held each week. Screening is pe r fo rmed by trained senior radiographers working on the project. An administrator enters the partici- pant ' s details, and answers to a brief quest ionnaire including details of family history and smoking, on arrival. Blood pressure, height and weight are recorded.

The results of the ul t rasound scan, including aortic d iameter and any difficulty in obtaining a satis- factory scan, are entered directly into a portable com- puter at the time. All abnormal results are immedi- ately notified individually to the participant 's GP, whilst normal scans and non-at tenders are sent as lists.

Follow-up policy is as detailed in Table 1. The diameter ranges chosen are based on previously pub- lished studies, but with an empirical component , as there is no universal agreement for these bands. Fur ther longitudinal screening studies are needed to

Table 1. The management of patients" initial aortic diameter detected on ultrasound screening

Aortic diameter

~<2 cm (age >80 years)

~<2.4 cm (normal)

>~2.5 cm and ~<2.9 cm (pre- aneurysmal dilatation)

~>3cm and ~<4.5cm (small aneurysm)

/>4.6 cm (established aneurysm)

Management

No further action

Rescan in 5 years

Rescan in 1 year

Rescan in 6 months

Consider referral to a vascular surgeon

hone the definitions. If the aortic d iameter is equal or greater than 4.6 cm, it is suggested to the participant 's GP that referral of the individual to a vascular sur- geon would be appropriate, but the final decision is left up td him or her. This gives au tonomy to the pr imary health-care professionals, which we have found useful in encouraging their cont inued partici- pation. The project compute r database also holds information on patients w h o undergo surgery for aor- tic aneurysm or who die with rup tu red aneurysm dur ing the project, whe the r screened or not.

R e s u l t s

A target list of 4264 individuals was supplied for review by their general practitioners. One-hundred- and-n ine teen men were excluded due to severe ill- health by this prescreening process, as described above.

Over a period of 18 months , 4145 individuals were asked to at tend for aortic u l t rasonography and 3030 (73%) have a t tended (Fig. 1). Between 50 and 64

2500

2000

1500 8

1000

500

z

50--64 years 65-79 years i> 80 years

Patient age groups

Fig. 1. The attendance rates of patients invited for screening by age groups. Patients contacted ([]); patients attending (B).

years, 2427 were contacted and 1776 a t tended (73%). Between 65 and 79 years, 1417 were contacted and 1061 a t tended (75%). For 80 years and over, 301 were contacted and 193 (64%) a t tended-s ignif icant ly less (p = 0.01-0.001) than the other two age bands, be- tween which there was no statistically significant difference.

For all individuals screened the mean aortic di- ameter was 2.1cm. A normal aortic d iameter (~<2.4cm) was found in 93.7% (n = 1664) aged 56-64

Eur J Vasc Surg Vol 8, March 1994

158 G.E. Morris et aL

12.5

10

~D

*~ 7.5

~ 2.5

0 2 . 5 - 2 . 9 cm 3 . 0 - 4 . 5 cm ~ 4.6 cm

Aort ic d iameter s

Fig. 2. The frequency of abnormal aortic diameters detected by ultrasound screening, grouped by age. 50-64 years ([]); 65-79 years (E3); 80 years and over (B).

years, 83.2% (n = 882) aged 65-79 years and 76.7% (n = 148) aged I>80 years.

Abnormal aortic d iameter distribution was as follows (Fig. 2). Pre-aneurysmal dilatation (2.5- 2.9cm) was found in 4% (n = 71) aged 50-64 years, 8% (n = 85) aged 65-79 years, and 11.4% (n = 22) aged/>80 years. A small aneu rysm (3.0-4.5 cm) was found in 2% (n = 35) aged 50-64 years, 6.3% (n = 67) aged 65-79 years, and 7.8% (n = 15) aged i>80 years. An established aneurysm (~>4.6cm) was found in 0.3% (n = 6) aged 50-64 years, 2.5% (n = 26) aged 65- 79 years, and 4.1% (n = 8) aged I>80 years.

Thus 335 participants (11.1%) were found to have an aortic d iameter greater than 2.5cm: 112 (6.3%) aged 50-64 years, 178 (16.8%) aged 65-79 years, and 45 (23.3%) aged 80 years and over. Over- all, 40 participants (1.3%) have been found to have an established aortic aneurysm (diameter ~>4.6cm). Further analysis of participants in the 50 to 64 year old group with abnormal aortic diameters is shown in Table 2. The group is d ivided into subgroups of 5-

Table 2. N u m b e r s of abnormal aortic diameters detected

Aortic diameter Subgroup age 2.5-2.9 cm 3.0-4.5 cm />4.6 cm

50-54 years 14 2 0

55-59 years 22 10 4

60-64years 35 23 2

year bands. The f requency of abnormal aortic diam- eters increases substantially after 55 years.

The Body Mass Index has been calculated for all participants [weight(kg)/heighta(m)]. There is no

Table 3. Aortic diameter v s . mean b o d y mass index

Aortic diameter Mean body mass index

42.4 cm 26.4

~2.5cm 26.9

marked difference be tween individuals with a normal aortic d iameter and those with an abnormal aortic d iameter (see Table 3).

During follow-up of the cohort, 144 individuals have been offered a second scan, and 135 (94%) a t tended. Forty-two individuals have been offered a third scan, and all a t tended. Three individuals have been offered a fourth scan, and all a t tended. In the normal aorta group, 14 individuals have been offered fur ther scans (to verify diameters), and 12 (86%) accepted. In the pre-aneurysmal dilatation group, 51 individuals have been offered fur ther scans, and 44 (86%) accepted. In the small aneurysm group, 74 in- dividuals have been offered fur ther scans, and all have accepted. In the established aneurysm group, five individuals have been offered fur ther scans, and all have accepted.

A total of 135 individuals have been rescanned. An apparen t size increase was recorded in 45 cases (initial diameters ranged from 2.0-6 .0cm), wi th a m ean change of 0.3 cm (range 0.1-1.0 cm). An appar- ent decrease in diameter was recorded in 56 cases (initial diameters ranged from 2.5-4 .6cm), with a m ean change of 0 .4cm (0.1-1.5cm). No change of d iameter was recorded in 32 cases. These results are wi thin accepted levels of reproducibili ty and observer variation. 17'1s No conclusions may be d rawn for t rends in size increase on 6-month rescanning so far.

Six individuals died dur ing the per iod of the s tudy. One dea th occurred in the 50-64 year old group, aortic d iameter was 2.9cm. Aortic rup ture was not the cause of death. Two deaths occurred in the 65-79 year old group, with aortic diameters of 3.0 and 3.5 cm. Aortic rupture was not the cause of dea th in ei ther case. Three deaths have occurred in the 80 years and over group. One of these participants died f rom a myocardial infarct 10 days after elective repair of a 12 cm inf lammatory AAA. Another part icipant d ied wi th a k n o w n aortic d iameter of 2.2cm. The other dea th was of an individual w h o did not a t tend his appo in tmen t for screening and the cause of dea th is u n k n o w n .

To date, 24 aneurysms have been opera ted on, wi th one fatality, as detailed above. Two of these aneurysms have been diagnosed in participants u n d e r 60 years of age.

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AAA Screening for All Males over 50 Years 159

Discussion

The methods we have used to induct individuals into the study has resulted in a satisfactory compliance rate of 73%, which compares favourably with the re- ported attendance rate of 43% after a single unsolici- ted letter. 19 Involving general practitioners gives closer links with the participants. Our compliance rate over 18 months is not quite as high as the rate over 2 years reported by Lucarotti et al. (79%) where scanning was performed at the individual practices, 2~ but it is comparable with the figure of 76% for the first 12 months of screening from the same group. 29 This suggests that as the project proceeds, the local popu- lation come to understand the concept and readily embrace it. This view is supported by our individual discussions with participants. It is encouraging to note that we had a 94% acceptance rate for second scans and 100% for subsequent scans.

Our acceptance rates for aneurysm screening compare favourably with other types of screening programmes-- the Nottingham faecal occult blood study for colorectal cancer reported an initial 37% compliance rate and the NHS breast screening pro- gramme currently runs at 71%. 3°"31

The attendance rate for younger individuals (50- 64 years) of 73% was not significantly different from those of the middle group (65-79 years) of 75%. This demonstrates unexpectedly good motivation in the younger group, and supports the idea of broadening the age range for screening, to allow specific target- ting of at-risk individuals at a younger age.

The compliance rate of 64% in our 80 years and above group, although low, is still substantially better than the 29% reported by Collin et al. for men of 75 to 79 years. 19 In some cases the lower acceptance rate in this older group is because these individuals reject an investigation that may culminate in their undergoing major surgery. This has implications for both elective and emergency AAA surgery in this cohort. Careful selection for repair is vital for this age group and patients would appear to recognise this. 32

The distribution of aortic diameters in the 65-79 year group is similar to that found in previously re- ported studies. 5" 16, 29, 33

In the younger group the finding that 6.3% of participants had abnormal diameters is important. Even though only six participants in this group were found to have established AAAs, the finding lends strong support for extending the range of screening, so that young men at risk of expanding AAA can be screened at intervals and timely intervention made when necessary. The sub-group analysis of abnormal diameter distribution suggests that it might be more

cost-effective to start screening at 55 years; however we will need to analyse the data after 3 years at the end of the pilot study to confirm this.

An aneurysm pick up rate of 11.9% in the 80 years and over group (including both small and established AAAs) is again a justification for extend- ing screening. Results from other reported series suggest that selected elective repair is worthwhile for these individuals. 23'2s It is too early to say in this study whether our results will support this, as only eight have undergone repair, with one early fatality. However the advent of less invasive, intraluminal techniques of AAA repair offer the potential of excel- lent outcomes for the older, more frail patient. 34

Expected annual growth rates of small aneur- ysms are now being established, the majority increas- ing by approximately 0.2 cm or less per year. 35' 36 This gives potential for greater economic benefits if screen- ing is extended to all men of 50 (or 55) years and above, as interval screening may be directed specifi- cally towards at-risk individuals. 22 Caution must be exercised however, as Sterpetti et al. reported an un- predictable sub-group exhibiting sudden increase in small aneurysm diameter. 37 They were unable to identify an independent predictor for the rate of diameter change, but suggested that recording the ratio of unaffected aortic diameter to dilated segment diameter in an individual may be helpful. Our follow- up screening protocol is more stringent than that pre- viously suggested, but by closer monitoring, we look forward to providing further data to help identify this sub-group, and to gain information on the natural history of all early aneurysms.

In conclusion, these early results support the continuation of our study into extending screening for AAA to a broader age range.

Acknowledgements

This study has been funded by a Public Health Operational Research Grant from the East Anglian Regional Health Authority. Particular thanks are given to Jo Tricklebank, senior radiographer, who set up the screening clinic and Nichola Lovell, administrator to the project.

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Accepted 18 November 1993

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