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  • TEC1: What is Screening?
  • TEC2: Are there different strategies for Abdominal Aorta Aneurysm Screening? Jump to
  • TEC3: Has any technical device for the detection of AAA established as internationally accepted golden standard? Jump to
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What is Screening?

Authors: Daniela Pertl, Sophie Brunner-Ziegler

Internal reviewers: Pseudo110 Pseudo110, Pseudo71 Pseudo71

Background information on screening as an intervention

The following table gives an overview of differences between screening practices. Details are described below.

Table 1: Overview and separation of screening strategies

What is the name of the intervention?

Population-based systematic screening

Various opportunistic screening practices

Synonyms

Mass/mass public health/selective/multiple/multiphasic screening for the whole population or of selected high risk groups in the population.

Selective/individual/multiple screening for individuals/individual approach

What is the objective of screening?

To identify a disease or condition in its preclinical and therefore potentially curable stage in apparently healthy people or people believing themselves to be healthy.

What are the requirements for screening?

Please see criteria in detail below.

How is it implemented?

Please see details below.

How is the screening organised?

Systematically

Not systematically:

a)      Screening is done occasionally during routine healthcare examinations, while the patient has no symptoms of the disease for which screening is carried out.

b)      Screening is done only for those patients that consult the physician because of symptoms.

How is it realised?

a)      Quality assured and evidence based screening programme that includes all relevant interventions to reduce risk.

Individual medical investigations, including screening test and interventions.

b)      Individual medical investigations, including screening test and interventions.

Who is screened?

a)      Every person in the entire population.

Screening is not population based: only individuals are screened.

b)      Selective screening approaches: target subgroups of the population with a high prevalence of risk factors for a certain disease or condition.

Where is screening done?

a)      Inpatient.

b)      Outpatient.

Outpatient;

Occasionally screening during routine healthcare examinations, such as periodic primary care visits (usual care).

Who screens?

a)      Medical technical assistants,

b)      General practitioners,

c)      Medical doctors who specialise in internal medicine.

a)      General practitioners,

b)      Medical doctors who specialise in internal medicine.

What are limitations of screening?

Please see details below.

How is it financed?

Depends on the screening strategies and healthcare systems (please see below).

History of Screening

The first routine investigations in healthy people were done around 1860 concurrently in the UK and the USA. At that time the main purpose was to gain new scientific insights into diseases and their prevention. Routine investigations were rapidly accepted in the USA because of the endorsement of insurance companies, who wanted to minimise the health risk profiles of their members, employers who wanted to ensure a healthy workforce and increase productivity, and because of medical scientists, who wanted to continue their pioneering task even if neither the health-related, nor the financial benefit of such routine investigations was clear at the beginning. In Europe, the need for quality assured and informed screening programmes has become more accepted since 1960. Current and future challenges to screening involve the weakened traditional authority of medical science, the changing risk awareness of the population, the advancement of genetic research, the decentralisation of healthcare and the growing financial burden of healthcare costs. {1}

Definition of Screening

The definition of screening and what people really mean when they use the term screening varies widely between professional groups and with time and local conditions. The primary objective of medical screening is to identify a disease or condition in its preclinical and therefore potentially curable stage in apparently healthy people or people believing themselves to be healthy.

For identification of a disease or condition, individual screening tests or a quality assured and evidence based screening programme, which includes all relevant interventions to reduce risk, can be applied. Additionally, every person in the entire population, or a target subgroup of the population with a high prevalence of risk factors for a certain disease or condition, can be included for screening. Furthermore, screening can be implemented in the inpatient or outpatient sector and executed by different experts. On the basis of the screening results people may be offered information, further assessments and/or appropriate therapy. {2, 3}

Screening does not apply to investigations, performed at a time when signs and symptoms of a disease have already occurred. However, there are some tests and investigations, which are carried out in healthy people and fulfil some criteria of screening programmes, but are not defined as having screening as their primary intention, for example occupational investigations at a workplace, preliminary investigations before operation, epidemiological surveys, lifestyle and fitness assessments or investigations for secondary disease. {1}

Requirements for screening

Before starting to plan and implement screening practices for a condition or disease, it is important to check if the criteria for viability, effectiveness and appropriateness are fulfilled. In 1968, the World Health Organization published principles and practices of screening for disease and listed some basic criteria that should ideally be fulfilled: {4}

  1. The condition or disease should be an important health problem.
  2. An accepted and effective treatment should be available.
  3. Facilities for diagnosis and treatment should be available.
  4. The condition or disease should have a recognisable latent or early symptomatic stage.
  5. There should be a suitable test or examination.
  6. The test should be acceptable to the population.
  7. The natural history of the condition, including development from latent to declared disease, should be adequately understood.
  8. There should be an agreed policy on whom to treat as patients.
  9. The screening cost should be economically balanced in relation to total medical expenditures.
  10. Case-finding should be a continuing process and not a "once and for all" project.

Additionally, detailed criteria, developed by the UK National Screening Committee, are available online http://www.screening.nhs.uk/criteria. {2}

Implementation of a screening programme

How a screening programme should be or is implemented depends on healthcare systems, strategies, medical services offered and financing of the screening programme. Essential elements that influence improvements in the health of a population as a result of implementing a screening programme are listed below. {1, 5}

  • Coordination and project management of the screening strategy.
  • Setting up objectives (in general and in detail) and policy.
  • System development and information management.
  • Constituting operative methods.
  • Quality assurance.
  • Analysis and assessment of evidence; assigning new research.
  • Screening equipment (equipment needed; equipment default set up; safety, compliance and quality assurance on machines; equipment review and replacement; transport of equipment; storage; consumables and other items needed; cleaning; packing up instructions).
  • Accommodation requirements (clinic rooms, screening office, etc.).
  • Organisation of public relations (leaflets, website, poster, etc.).
  • Identification of relevant people.
  • Invitation of relevant people.
  • Information and consultation of participants.
  • Staff requirements (for example: project management team, [clinical] leader, clinicians, consultants, clinical skills trainer, screening staff, screening technicians, nurse practitioners, coordinator, clerical officer for administration, medical physicist, IT lead, other organisations, etc.) and responsibilities.
  • Workforce education and training.
  • Realisation of diagnostic investigations and screening tests.
  • Statistical evaluation of the realisation of screening.
  • Carrying out necessary interventions/treatment after screening.
  • Documentation (screening process, test results, appointments, following treatment, use of data, administration, consent declined or withdrawn, storage and transfer of person-identifiable data, incident reporting, etc.).

Screening Practices

The following types of screening can be undertaken.

  1. Population-based systematic screening

a) Population based approaches that attempt to systematically screen every person in the entire population.

b) Selective screening approaches that target subgroups of the population with a high prevalence of risk factors for a certain disease or condition.

The process of population-based systematic screening can be divided into the following stages {5}:

  • identification of the relevant cohort  
  • invitation of eligible people  
  • informing eligible people about screening before the decision to participate or not is taken
  • testing the people entering the screening programme (the programme ends at this point if the test results are within normal limits)  
  • surveillance and forward planning if a risk for the disease exists but no immediate treatment is needed  
  • diagnosis of the disease and further actions  
  • treatment or intervention, taking into account valid guidelines  
  • monitoring outcomes
  1. Various opportunistic screening practices/usual care

(a)    The physician screens individuals occasionally during routine healthcare examinations (selective screening for individuals). The patient is presumed well or is not complaining of the disease for which screening is offered. The physician has no special reasons to suspect illness but complies with an accepted standard of good diagnostic practice.

(b)   The physician examines only those patients who consult him or her because of some complaints.

For various opportunistic screening practices for AAA no specified screening process is defined. In most cases, it is done in the primary care setting as an add-on investigation to other primary prevention investigations, or an AAA may occasionally be detected when a different indication is primarily being examined by the practitioner.

Screening in practice

Population-based systematic screening and various opportunistic screening practices can consist of {1, 6}

(a) individual medical investigations, including screening tests and interventions which altogether result in a screening programme or

(b) quality assured and evidence based screening programmes, which include all relevant interventions to reduce risk.

The implementation, realisation and financing of screening vary between the different screening practices and healthcare systems {1}:

  • Governmental financing and offering of quality assured and evidence based national screening programmes (e.g. UK).
  • Governmental reimbursement of costs for recommended screening interventions by independent or national providers (e.g. Australia).
  • Only some health insurance agencies offer recommended screening from specified providers. Patients must decide whether they can afford it (e.g. USA).

Additional Benefits of AAA-screening

Detection of AAA by any screening procedure may act not only as a decision tool for planning elective surgery but also as a tool to intensify and supervise lifestyle modifications for the patient (i.e. smoking cessation, optimising antihypertensive pharmacotherapy,…).

Limitations of AAA-screening

The implementation of screening practices has the potential to save lives or improve quality of life because of early diagnosis of serious diseases or conditions, but it cannot guarantee protection. In any screening practice, there is a potential for harms and adverse events for patients, e.g. during the screening test, during diagnosis or during treatment. There is, for example, the potential for false positive results in individual screening tests, which may be a considerable psycho-social burden for those concerned. Additionally, false positive results can result in unnecessary investigation and treatment. On the other hand, false negative results delay the detection and final diagnosis of a disease. During the screening test, patients could be exposed to radiation or chemicals or undergo discomfort, stress or anxiety, all of which could lead to adverse effects. Therefore it is essential to establish whether, in practice, screening a healthy (risk) population leads to an improvement of relevant outcomes. {2, 7}

Critical
Partially
Pertl D, Brunner-Ziegler S Result Card TEC1 In: Pertl D, Brunner-Ziegler S Description and technical characteristics of technology In: Jefferson T, Vicari N, Frønsdal K [eds.]. Abdominal Aorta Aneurysm Screening [Core HTA], Agenzia nationale per i servizi sanitari regionali (age.na.s), Italy; 2013. [cited 28 May 2023]. Available from: http://corehta.info/ViewCover.aspx?id=106

Are there different strategies for Abdominal Aorta Aneurysm Screening?

Authors: Daniela Pertl, Sophie Brunner-Ziegler

Internal reviewers: Pseudo110 Pseudo110, Pseudo71 Pseudo71

For abdominal aortic aneurysm screening different practices exist (population-based systematic and various opportunistic screening practices). In most countries no systematic and nationwide screening programme is implemented. Decisions about screening are made individually by primary care physicians. In addition, several cardiovascular societies have published recommendations concerning who should be screened and under which conditions. All of the recommendations require clinicians to individualise care and recommendations depending on the patient's risk and likelihood of benefit.

The following table gives an overview of the AAA screening strategies of various countries {8}.

Table 2: Overview of country-specific AAA screening practices

Country

Screening practice

Details

Austria

No specific screening programme for AAA.

 

Belgium

No specific screening programme for AAA.

 

Croatia

No specific screening programme for AAA.

If AAA is occasionally found during other examinations, these patients will be referred to a vascular surgeon.

Finland

No specific screening programme for AAA.

Population-based screening for AAA is currently under serious consideration, but no decisions have been made.

Germany

No specific screening programme for AAA.

 

Latvia

No specific screening programme for AAA.

 

Lithuania

Opportunistic screening.

In individuals who have sought medical advice for a specific symptom or complaint the opportunity is taken to suggest screening. It is undertaken during a clinical consultation because of another health problem or condition.

Spain

No specific screening programme for AAA.

 

Sweden

Population-based screening programme.

Screening of a defined healthy population (based on a defined  risk profile/eligible population) by invitation to a screening programme.

United Kingdom

Population-based screening programme.

The NHS Abdominal Aortic Aneurysm (AAA) Screening Programme is being gradually introduced across England and will be fully in place at the end of 2013 (one-time ultrasound scan examination for men aged 65).

In Northern Ireland, Scotland and Wales these screening programmes are currently in the preparatory stages.

United States of America

Population-based screening programme.

Medicare covers one-time screening ultrasound for AAA if the patient gets a referral for it from a physician or other qualified non-physician practitioner as a result of the "Welcome to Medicare" preventive visit within the first 12 months of having Medicare Part B.

Patients are eligible for AAA screening if they have a family history of AAA, and/or if they are a man, aged 65 to 75 who has smoked at least 100 cigarettes in his lifetime and has never had an AAA ultrasound screening paid for by Medicare. {9, 10}

Published guidelines on AAA screening attempt to close the gap between the best available evidence and what physicians do in their practices. In their systematic review of guidelines on abdominal aortic aneurysm screening, Ferket et al. (2012) {11} identified seven relevant guidelines and the quality of development of each guideline included was determined by the Appraisal of Guidelines Research and Evaluation (AGREE) instrument. The AGREE instrument is a validated tool to evaluate the process of practice guideline development and the quality of reporting. {12}

Table 3: Guidelines on AAA screening (Ferket et al. 2012) {11}

Guideline-Nr.

Title (author, year)

Country that guideline applies to

AGREE rigour score

1

Screening for abdominal aortic aneurysm: recommendation statement (US Preventive Services Task Force 2005)

USA

79%

2

ACC/AHA 2005 practice Guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): a collaborative report from the American Association for Vascular Surgery/Society for Vascular Surgery, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines (Hirsch et al. 2006)

USA

63%

3

Abdominal aortic aneurysm screening (UK National Screening Committee 2007)

UK

41%

4

Screening for abdominal aortic aneurysm in Canada: review and position statement of the Canadian Society for Vascular Surgery (Mastracci et al. 2007)

Canada

40%

5

Canadian Cardiovascular Society Consensus Conference: peripheral arterial disease 2 executive summary (Abramson et al. 2005)

Canada

38%

6

The care of patients with an abdominal aortic aneurysm: the Society for Vascular Surgery practice guidelines (Chaikof et al. 2009)

USA

25%

7

Screening for abdominal aortic aneurysm: a consensus statement (Kent et al. 2004)

USA

17%

Details of guidelines on AAA screening included in the systematic review of Ferket et al. {11} are reported below.

Table 4: Details of Guidelines on AAA screening (Ferket et al. 2012) {11}

Guideline no. (for details see Table 3)

Target group

Screening practice

Primary screening test

Screening intervals

Recommendation

1

a) Men aged 65-75 who have ever smoked

b) Men aged 65-75 who have never smoked

c) Women

Opportunistic screening/case-finding

Abdominal ultrasonography

One-time screening

a)    For men aged 65-75 who have ever smoked

b)    Not for, not against men aged 65-75 who have never smoked

c)Against women

2

a) Men aged ≥ 60 who are siblings/offspring of patients with AAAs

b) Men aged 65-75 who ever smoked

Not reported

Abdominal ultrasonography; physical examination

One-time screening

For

3

Men aged 65

Population-based/mass screening

Abdominal ultrasonography

One-time screening

For

4

a) Men aged 65-75, who are candidates for surgery and are willing to participate

b) Women aged >65 and multiple risk factors (family history of AAA, smoking history, cerebrovascular disease, age >70)

c) Women aged >65, adult population aged <65 years

d) Men aged >75 years and multiple risk factors

a)    Population-based/mass screening

b)    Individualised investigation

c)     Population-based/mass screening

d)    Individualised investigation

Abdominal ultrasonography

No follow-up ultrasound is necessary before 3-5 years if aortic diameter <3.0 cm

a) For

b) Consider

c) Against

d) Consider

5

a) Men aged 65-74

b) Women aged 65 with cardiovascular disease and positive family history of AAA

c) Men aged ≥ 50 and positive family history of AAA

Population-based/mass screening

Abdominal ultrasonography

Repeat ultrasound follow-up in 3-5 years if aortic diameter <3.0 cm

For

6

a) Men aged ≥65

b) Men aged ≥55 and family history of AAA

c) Women aged ≥ 65 and family history of AAA or who have smoked

Population-based/mass screening

Abdominal ultrasonography

One time screening if aortic diameter <2.6 cm

For

7

a) Men aged 60-80

b) Women aged 60-85 and cardiovascular risk factors

c) Men and women aged >50 and family history of AAA

Population-based/mass screening

Abdominal ultrasonography

One time screening if aortic diameter <3.0 cm

For

The US Preventive Services Task Force (USPSTF) {7} recommends one-time screening for abdominal AAA by ultrasonography in all men aged 65 to 75 years, who have smoked at least 100 cigarettes in their lifetime. This recommendation is based on the evidence that surgical repair of large AAAs (5.5 cm or more) on the basis of screening leads to decreased AAA-specific mortality and therefore outweighs screening-associated harms in this population group. The USPSTF states that the harms of AAA-screening in men aged 65 to 75 years, who have never smoked, in men aged more than 75 years and in women in general balance or outweigh the benefits. Men aged more than 75 years are at higher risk for AAAs, but the increased presence of comorbidities and limited life expectancy decreases the likelihood that they will benefit from screening.

Summarizing the systematic review of guidelines from Ferket et al. (2012) {11} shows that most of the seven included guidelines contain recommendations that favour one-time AAA screening for men aged 65 years and older. Every guideline reasoned that abdominal ultrasonography is the primary screening test. Only one guideline group (ACC) recommended physical examination as a useful screening tool in addition to ultrasonography. The guidelines did not agree on whether a smoking history should be present or not. Additionally, four guidelines (three of them had low AGREE scores) contained disparate recommendations on screening women and middle-aged men at elevated risk, whereas guidelines with higher AGREE scores did not. The criterion for elective surgical repair in elderly men for an abdominal aortic diameter of 5.5 cm was unanimously used but there was no consensus on the management of smaller AAAs.

Most of the guidelines give recommendations for surveillance of patients with aneurysms smaller than 5.5 cm in diameter but these recommendations vary in the intensity of follow up and the cut-off points of the aorta diameter. For example, some guidelines recommend that an annual abdominal ultrasound is acceptable if the AAA is 3.0 to 4.4 cm. Others recommend that if the AAA diameter is between 4.0 and 5.4 cm, surveillance should be done every 6 to 12 months. If the AAA is <3.0 cm, some guidelines recommend no follow-up surveillance before 3 to 5 years. Other guidelines say that aneurysms 3.0 to 3.9 cm in diameter should be surveyed every 2 to 3 years, and those 4.0 to 5.4 cm in diameter should be assessed every 6 months. {11}

The typical expansion rate of AAA is around 0.3-0.4 cm per year, on average. As the expansion rate of AAAs is positively correlated to size, surveillance intervals should depend on size. As a patient's health status may change during the surveillance period, continued AAA surveillance should occur only if the patient remains a good surgical candidate and has a reasonable life expectancy. If the first-time ultrasonography screening for AAA revealed normal aortic diameter, there is no need for re-screening, as negative results appear to virtually exclude the risk for future AAA rupture. {9}

In conclusion, even if the officially accepted cut-off point for elective surgery has been set to an aneurysm size of 5-5.5 cm, the final decision about going ahead with a surgical procedure must be considered individually taking into account the option of endovascular treatment, age, comorbidities and other factors.

Question refers partly to RC-CUR10, RC-EFF24.

Important
Partially
Pertl D, Brunner-Ziegler S Result Card TEC2 In: Pertl D, Brunner-Ziegler S Description and technical characteristics of technology In: Jefferson T, Vicari N, Frønsdal K [eds.]. Abdominal Aorta Aneurysm Screening [Core HTA], Agenzia nationale per i servizi sanitari regionali (age.na.s), Italy; 2013. [cited 28 May 2023]. Available from: http://corehta.info/ViewCover.aspx?id=106

Has any technical device for the detection of AAA established as internationally accepted golden standard?

Authors: Daniela Pertl, Sophie Brunner-Ziegler

Internal reviewers: Pseudo110 Pseudo110, Pseudo71 Pseudo71

Ultrasonography as gold standard

Ultrasonography has been established as the gold standard technical device for screening for AAA. Different investigations show that ultrasonography is a valid diagnostic technique for the detection of AAA with both sensitivity and specificity of nearly 100%. The test is non-invasive, relatively inexpensive and fast, and patients are not exposed to ionizing radiation. Additionally, this test is highly acceptable to patients. {13-17}

More than 80% of all AAAs are detected occasionally or through ultrasonography screening {18}. If an AAA is suspected or if an AAA is detected through ultrasonography screening, further medical investigations are carried out to verify the diagnosis and define treatment, for example, computed tomography (CT) or magnetic resonance imaging (MRI).

For detection of AAAs, other diagnostic technologies, besides ultrasonography, are also used. For example abdominal palpation, CT or MRI (see result card TEC 8, {8, 13, 19}) but ultrasonography is the detection method of choice for AAA screening {13-17}.

For ultrasonography various image-guided methods are available, such as the colour-coded duplex sonography that is most often used. In brief, colour-coded duplex sonography is an ultrasound-based imaging method, using high-frequency sound waves to reflect the structure of inner organs or blood vessels. A computer receives these reflected waves and uses them to create a picture, visualizing possible pathology. Most devices can additionally study the relative velocity of the blood flow or whether the blood flow is moving towards or away from the transducer. Such measurements are based on the Doppler effect (which, within certain limits allows the accurate assessment of the direction and velocity of the blood flow by calculating the frequency shift of the flow-wave and visualizing it in colour). However, currently no standards for the display of colour-coded duplex sonographic images are available. Some laboratories use red to display arterial vessels and blue to display venous vessels; others use colours to indicate the direction of the flow either towards the transducer or away from it. To interpret the results, knowledge of the physiology and pathophysiology of blood flow in the body is therefore important. {20}

Throughout Europe, Siemens Healthcare and GE Healthcare are currently the leaders in the distribution of colour-coded duplex-sonographic technical devices. {21} Figure 1 shows an example of such a device, including the monitor and keyboard.

Figure 1: Colour-coded duplex-sonographic technical device

pdf106.Figure 1

Figure 2 shows the duplex sonographic documentation of the transverse diameter of an infrarenal abdominal aortic aneurysm. The black area within the arrows represents the lumen of the expanded aorta.

Figure 2: Duplex sonographic documentation of an AAA

pdf106.Figure2

Figure 3 illustrates the transverse diameter of an infrarenal abdominal aortic aneurysm in colour-coded mode. The red colour represents arterial blood flow.

Figure 3: Transverse diameter of an AAA

pdf106.Figure3

Question refers partly to RC-EFF24, RC-EFF25.

Important
Partially
Pertl D, Brunner-Ziegler S Result Card TEC3 In: Pertl D, Brunner-Ziegler S Description and technical characteristics of technology In: Jefferson T, Vicari N, Frønsdal K [eds.]. Abdominal Aorta Aneurysm Screening [Core HTA], Agenzia nationale per i servizi sanitari regionali (age.na.s), Italy; 2013. [cited 28 May 2023]. Available from: http://corehta.info/ViewCover.aspx?id=106

References