Final Research Plan

Abdominal Aortic Aneurysm: Screening

November 30, 2017

Recommendations made by the USPSTF are independent of the U.S. government. They should not be construed as an official position of the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.

Expand All
Panel 1

The final Research Plan is used to guide a systematic review of the evidence by researchers at an Evidence-based Practice Center. The resulting Evidence Review will form the basis of the USPSTF Recommendation Statement on this topic.

The draft Research Plan was available for comment from August 10 until September 6, 2017 at 8:00 p.m., ET.

Figure 1 is the analytic framework that depicts the five Key Questions to be addressed in the systematic review. The figure illustrates how screening for abdominal aortic aneurysm (AAA) may result in improved health outcomes, including reducing AAA-specific and all-cause mortality, as well as aneurysm rupture rate (KQ1). Additionally, the figure depicts the effects of rescreening for AAA on health outcomes or AAA incidence in a previously screened, asymptomatic population (KQ2), as well as harms associated with one-time and repeated screening (KQ3). Further, the figure illustrates how treating small AAAs (i.e., aortic diameter of 3.0 to 5.4 cm) with pharmacotherapy or surgery effects treatment-relevant intermediate health outcomes (KQ4) and what harms are associated with these treatments (KQ5).

Abbreviation: AAA=abdominal aortic aneurysm.

  1. What are the effects of one-time screening for abdominal aortic aneurysm (AAA) on health outcomes in an asymptomatic population age 50 years or older?
    1. Do the effects of one-time screening for AAA vary among subpopulations (i.e., by sex, smoking status, age, family history, or race/ethnicity)?
  2. What are the effects of rescreening for AAA on health outcomes or AAA incidence in a previously screened, asymptomatic population without AAA on initial screening?
    1. Do the effects of rescreening for AAA vary among subpopulations (i.e., by sex, smoking status, age, family history, or race/ethnicity)?
    2. Do the effects of rescreening for AAA vary by the time interval between screenings?
  3. What are the harms of one-time and repeated screening for AAA?
    1. Do the harms of one-time and repeated screening for AAA vary among subpopulations (i.e., by sex, smoking status, age, family history, or race/ethnicity)?
  4. What are the effects of treatment (pharmacotherapy or surgery) on treatment-relevant, intermediate health outcomes in an asymptomatic, screen-detected population with small AAAs (i.e., aortic diameter of 3.0 to 5.4 cm)?
    1. Do the effects of treatment vary among subpopulations (i.e., by sex, smoking status, age, family history, or race/ethnicity)?
  5. What are the harms of treatment in an asymptomatic, screen-detected population with small AAAs (i.e., aortic diameter of 3.0 to 5.4 cm)?
    1. Do the harms of treatment of small AAAs vary among subpopulations (i.e., by sex, smoking status, age, family history, or race/ethnicity)?

Contextual questions will not be systematically reviewed and are not shown in the Analytic Framework.

  1. Are there externally validated risk models for screening for AAA?   
  2. Does the epidemiology or overall effectiveness of treatment of AAA differ by age, sex, smoking status, or family history?
  3. Does screening yield differ based on screening strategy (e.g., high-risk vs. low-risk populations)?
  4. If a patient has a computed tomography scan for another purpose and no AAA is identified, is that considered adequate screening for AAA, or should the patient be rescreened with ultrasound?

The Research Approach identifies the study characteristics and criteria that the Evidence-based Practice Center will use to search for publications and to determine whether identified studies should be included or excluded from the Evidence Review. Criteria are overarching as well as specific to each of the key questions (KQs).

  Included Excluded
Populations KQs 1–3: Asymptomatic adult population

KQs 4, 5: Asymptomatic adult population with small AAAs (i.e., aortic diameter of 3.0 to 5.4 cm)

 KQs 1–3: Patients experiencing symptoms related to AAA

KQs 4, 5: Patients experiencing symptoms related to AAA; populations with AAAs with an aortic diameter larger than 5.4 cm or smaller than 3.0 cm
Setting Studies conducted in primary care or other settings with a comparable population to primary care (e.g., general unselected population for screening [KQs 1, 3])  
Disease/condition AAA (aortic diameter ≥3.0 cm)  
Interventions KQs 1–3: Screening with ultrasound

KQs 4, 5: Treatment with pharmacotherapy (e.g., statins, angiotensin converting enzyme inhibitors, antibiotics) or surgical intervention

 KQs 1–3: Screening with physical examination, computed tomography, or magnetic resonance imaging
Comparisons KQs 1, 3: One-time screening vs. no screening

KQs 2, 3: Repeat screening vs. no rescreening

KQ 4: Pharmacotherapy vs. placebo, surgery vs. surveillance alone

 KQ 2: Comparison of surveillance interval 

KQs 4, 5: Comparative effectiveness of treatments
Outcomes KQs 1, 2: All-cause mortality, aneurysm-related mortality, cardiovascular disease mortality, aneurysm rupture rate, cardiovascular disease events, and quality of life

KQ 3: Anxiety and downstream procedures related to false-positive results

KQ 4: AAA annual growth rate, all-cause mortality, aneurysm-related mortality, cardiovascular disease mortality, aneurysm rupture rate, cardiovascular disease events, and quality of life

KQ 5: Harms (i.e., serious adverse events from pharmacotherapy or surgery)

  
Study Designs KQs 1, 4: Randomized, controlled trials

KQs 2, 3: Randomized, controlled trials; large cohort studies (sample size >1,000)

KQ 5: Randomized, controlled trials; large cohort studies (sample size >1,000); vascular surgery registries

 KQs 1, 4: Case-control, cross-sectional, and cohort studies; editorials, letters, and opinions; cost studies

KQs 2, 3: Case-control and cross-sectional studies; editorials, letters, and opinions; cost studies
Countries Studies conducted in countries categorized as "Very High" on the 2016 Human Development Index (as defined by the United Nations Development Programme) Studies conducted in countries that are not categorized as "Very High" on the 2016 Human Development Index
Language English only Languages other than English
Quality Fair- and good-quality studies Poor-quality studies

The draft Research Plan was posted on the USPSTF Web site from August 10 to September 6, 2017. In response to comments, the USPSTF expanded the scope of the evidence review to include cardiovascular events (e.g., myocardial infarction, stroke) and mortality related to cardiovascular disease to more fully evaluate the benefits and harms of treatment of small AAAs (i.e., with pharmacotherapy such as statins and antihypertension medications). The USPSTF made other minor modifications as appropriate, such as clarifying that surveillance alone will be included as a comparator for KQ 4. Suggestions for implementation of the evidence review were noted but did not change the scope of the review; therefore, they are not shown in this document.