Recommendations on Screening for Abdominal Aortic Aneurysm in Primary Care

Objectives

The guideline aims to prevent abdominal aortic aneurysm (AAA) rupture and AAA-related death through evidence-informed primary care screening recommendations for asymptomatic adults. It supports a one-time ultrasound screening offer for men aged 65 to 80 years, while emphasising that the expected absolute benefit has fallen as AAA prevalence has declined and that decisions should account for individual preferences and potential harms.[1][2][3]

• Offer one-time ultrasonography screening to men aged 65 to 80 years as a weak recommendation supported by moderate-quality evidence.[2][4]
• Reduce AAA-related mortality, rupture and emergency procedures, recognising that screening also increases total and elective AAA repairs.[5][6][7][8]
• Balance potential benefits against overdiagnosis and interventions for aneurysms that may never rupture; long-term evidence estimated overdiagnosis among screen-positive participants at 45%, or 17.6 patients per 1,000 people screened.[1][5][3]
• Advise against screening men older than 80 years through a weak recommendation based on low-quality evidence, because trial evidence is uncertain for this group and coexisting conditions may increase procedural risk.[2][5][3][4]
• Advise against screening women through a strong recommendation supported by very low-quality evidence, as the available trial evidence found no improvement in health outcomes and potential benefits are very small relative to procedural risks and opportunity costs.[5][3][4]
• Apply weak recommendations where the balance of benefits, harms, costs, feasibility, acceptability or equity is uncertain, and where further research could alter confidence in estimated effects.[9][3]

Implementation

The guideline uses an evidence-to-recommendation model combining systematic evidence review, Grading of Recommendations Assessment, Development and Evaluation (GRADE), stakeholder input and shared decision-making in primary care. It was developed by the Canadian Task Force on Preventive Health Care, supported by the Public Health Agency of Canada, with evidence-review support from McMaster University, expert advice, and knowledge-translation input for clinicians and patients.[1][10][11][12]

• Use ultrasonography as the screening modality, reflecting its established diagnostic performance and relative ease of use; delivery may occur in family physician settings where providers have appropriate training.[13][8]
• Base recommendations principally on pooled findings from four population-based randomised controlled trials of one-time ultrasonography in men aged 65 years and older, with evidence from England, Denmark and Australia and follow-up at three to five and 13 to 15 years.[10][2][13]
• Assess effects on AAA-related and all-cause mortality, rupture, emergency and elective procedures, overall repair, 30-day procedure-related mortality, quality of life and overdiagnosis.[10][2][5]
• Recognise that screening reduced AAA-related deaths by 1.3 per 1,000 men screened at three to five years and 3.2 per 1,000 at 13 to 15 years, corresponding to numbers needed to screen of 796 and 311.[2]
• Recognise that all-cause mortality showed little or no clear difference, whereas AAA rupture and emergency procedures were reduced and total and elective procedures increased.[6][7]
• Use GRADE to judge certainty of evidence and recommendation strength, considering benefits, harms, confidence in effect estimates, patient values and preferences, and resource use.[10][9][2]
• Conduct systematic and contextual literature searches, update evidence before publication, and obtain review from content experts, healthcare stakeholders and the full task force before external review.[9][2]
• Use the Feasibility, Acceptability, Cost and Equity tool to assess implementation considerations with stakeholders; stakeholders generally considered the recommendations feasible, acceptable, affordable and unlikely to worsen health equity.[9][14][3]
• Support shared decision-making with men aged 65 to 80 years, particularly where chronic conditions may worsen outcomes after elective repair, and discuss preferences with healthy men older than 80 years if elective repair would be relatively low risk.[1][3][8]
• Provide knowledge-translation tools developed with the Knowledge Translation Program at St Michael’s Hospital, informed by clinician and patient feedback and patient-preference research.[9][3][12]
• Monitor the proportion of eligible men whose primary care providers discuss screening, the number screened and screening outcomes, while tracking AAA epidemiology because declining prevalence may favour a more targeted approach.[8]
• Investigate whether outcomes differ for people who have ever smoked or have a family history of AAA, and assess the value of rescreening or population targeting by characteristics including race or ethnicity.[8]

Funding for the Canadian Task Force on Preventive Health Care was provided by the Public Health Agency of Canada, whose views did not influence guideline content; competing interests were recorded and managed.[11]The material provides no Canadian programme budget, financing plan, implementation cost or funding gap, although cited evidence found AAA screening cost-effective at an incremental cost-efficiency ratio below 30,000 US dollars per quality-adjusted life-year gained.[14][11]

Monitoring & Evaluation

Evaluation centres on the benefits and harms of one-time ultrasonography screening for abdominal aortic aneurysm (AAA), drawing principally on four population-based randomised controlled trials among asymptomatic men aged 65 years and older, with pooled outcomes reported at three-to-five and 13-to-15-year follow-up.[2][13]The guideline development process used systematic evidence review, GRADE evidence-to-decision considerations, expert input, stakeholder review and task-force approval, but does not establish a comprehensive routine implementation-monitoring or reporting system.[10][9][2]

• Assess AAA-related mortality, all-cause mortality, aneurysm rupture, emergency procedures, elective procedures, total AAA repair and 30-day mortality following emergency or elective procedures.[10][2][6][7]
• Use pooled trial evidence to estimate that screening produced 1.3 fewer AAA-related deaths per 1,000 men screened at three to five years and 3.2 fewer deaths per 1,000 at 13 to 15 years, corresponding to numbers needed to screen of 796 and 311.[2]
• Interpret reductions in AAA-related mortality using reported risk ratios of 0.57 at three to five years and 0.66 at 13 to 15 years, both supported by moderate-quality evidence.[6]
• Recognise that all-cause mortality showed little or no clear difference, with low-quality evidence at three to five years and moderate-quality evidence at 13 to 15 years.[6]
• Measure reductions in aneurysm rupture and emergency procedures alongside increases in total AAA procedures and elective repairs, for which the reported evidence quality was moderate.[6][7]
• Consider procedure-related outcomes: evidence found minimal or no difference in 30-day mortality after elective procedures and no difference in 30-day mortality after emergency procedures at either follow-up period.[5]Screening was also associated with 12.83 fewer deaths within 30 days of an AAA procedure per 1,000 people over three to five years and 5.63 fewer per 1,000 over 13 to 15 years.[14]
• Examine wider harms and patient-centred outcomes, including quality of life, overdiagnosis and changes in disease prevalence.[5]Quality-of-life studies found no statistically significant difference between screened and control groups, although the evidence was very low quality.[5]
• Account for overdiagnosis: 13-year follow-up from the Multicentre Aneurysm Screening Study estimated overdiagnosis at 45% of screen-positive participants, or 17.6 overdiagnosed patients per 1,000 people screened.[5]
• Monitor epidemiology because recent population-based studies estimated AAA prevalence among screened men older than 65 years at 1.5% to 1.7%, compared with 3.9% to 7.2% in the trials, potentially reducing the absolute benefit of age-based screening.[5][8]
• Track the proportion of men aged 65 to 80 years who discuss screening with primary care providers, the number screened and screening outcomes.[8]
• Investigate whether screening effects differ for people who have ever smoked or have a family history of AAA, and assess the potential value of rescreening overall or in selected groups, including groups defined by race or ethnicity.[8]
• Apply the Grading of Recommendations Assessment, Development and Evaluation system to judge confidence in effect estimates and the strength of recommendations, taking account of benefits, harms, values and preferences, and resource use.[10][9][2]
• Maintain methodological accountability through review by content experts and healthcare stakeholders, approval by the full task force, external review and development of knowledge-translation tools with clinician and patient feedback.[9][2]

No formal reporting schedule, named surveillance system, routine performance dashboard or explicit accountability mechanism for implementation is specified beyond the proposed discussion, screening and outcome measures and the guideline-development review processes.[2][14][8][11]

Costing & Financing

Cost and resource use were considered in developing the screening recommendations, but the material does not provide a Canadian programme budget, implementation cost, resource allocation, funding gap or financing plan.[9][2][11]The Public Health Agency of Canada funded the Canadian Task Force on Preventive Health Care, while its views were reported not to have influenced guideline content.[11]

• Consider resource use within the GRADE framework, which includes whether an intervention represents a wise use of resources.[10]
• Assess cost, feasibility, acceptability and equity through the Feasibility, Acceptability, Cost and Equity tool used with stakeholders during recommendation development.[9][2]
• Note that health-related stakeholders generally considered the recommendations feasible, acceptable and affordable, with no anticipated adverse effect on health equity and high intent to implement.[14][3]
• Recognise evidence reporting AAA screening as cost-effective at an incremental cost-efficiency ratio below 30,000 US dollars per quality-adjusted life-year gained, based on systematic reviews, a randomised controlled trial and modelling studies.[14]
• Consider the reported conclusion from a Swedish nationwide programme that screening remained cost-effective despite declining prevalence and a shift towards more expensive procedures.[14]
• Avoid inferring local affordability or fiscal impact from the cited economic evidence, as no Canadian cost-effectiveness model, budget impact assessment, funding source for delivery, implementation allocation or economic assumptions are supplied.[14][3][4][8]

Bibliographic material cites studies concerning cost-effectiveness and hospital costs, but provides no additional numeric economic estimates for this guideline.[15][16][17]