Fifteen-year follow-up of a randomized clinical trial of ultrasonographic screening for abdominal aortic aneurysms

BACKGROUND: Long-term benefits of screening for abdominal aortic aneurysm (AAA) are uncertain. These are the final results of a randomized controlled screening trial for AAA in men, updating those reported previously. Benefit and compliance over a median 15-year interval were examined. METHODS: One group of men were invited for ultrasonographic AAA screening, and another group, who received standard care, acted as controls. A total of 6040 men aged 65-80 years were randomized to one of the two groups. Outcome was monitored in terms of AAA-related events (surgery or death). RESULTS: In the group invited for screening, AAA-related mortality was reduced by 11 per cent (from 1.8 to 1.6 per cent, hazard ratio 0.89) over the follow-up interval. Screening detected an AAA in 170 patients; 17 of these died from an AAA-related cause, seven of which might have been preventable. The incidence of AAA rupture after an initially normal scan increased after 10 years of follow-up, but was still low overall (0.56 per 1000 person-years). CONCLUSION: Screening with a single ultrasonography scan still conferred a benefit at 15 years, although the results were not significant for this population size. Fewer than half of the AAA-related deaths in those screened positive could be prevented. Registration number: ISRCTN 00079388 (http://www.controlled-trials.com).     

Randomized clinical trial of screening for abdominal aortic aneurysm in women

BACKGROUND: Screening for abdominal aortic aneurysm (AAA) is commonly restricted to men. Recent studies have indicated a possible increase in deaths due to ruptured AAA in women, and a higher rate of rupture in women than in men. The present report details results from a randomized controlled trial that assessed the effects of screening women for AAA. METHODS: Some 9342 women aged 65-80 years were entered into the trial and randomized to age-matched screen and control groups. A single ultrasonographic scan was offered to women in the screening arm of the study. Women with an AAA received follow-up scans, and were considered for elective surgery if certain criteria were met. RESULTS: The prevalence of AAA was six times lower in women (1.3 per cent) than in men (7.6 per cent). Over 5- and 10-year follow-up intervals, the incidence of rupture was the same in the screened and control groups of women. CONCLUSION: Screening women for AAA is neither clinically indicated nor economically viable.     

Effectiveness and cost of screening for abdominal aortic aneurysm: results of a population screening program

OBJECTIVES: We undertook this study to calculate the cost per life-year gained in the first round of a screening program for abdominal aortic aneurysm (AAA) and to estimate the costs in a subsequent round. METHODS: This was an intervention study, with follow-up for ruptured aneurysms. Men older than 50 years were screened for asymptomatic AAA. Outcome measures included cost per life-year saved and number of men needed to be screened to save one life. RESULTS: The incidence of ruptured AAA was 2.6 per 10,000 person- years in the screening group and 7.1 per 10,000 person-years in the control group. Screening is estimated to have prevented 10.8 ruptured AAA and 8 deaths per year, gaining 51 life-years per year for the study population, and to have reduced the incidence of ruptured AAA by 64% (95% CI, 42%-77%). Each life-year gained during the first screening round cost $1107. To save one life, 1000 men need to be screened and 5 elective operations performed. We predict that a second round of screening can be cost neutral. CONCLUSIONS: The cost-effectiveness of screening for AAA compares favorably with screening programs for other disorders in adults.     

Ultrasonographic screening for abdominal aortic aneurysm.

OBJECTIVE--To assess the prevalence of abdominal aortic aneurysm in a selected group of men over the age of 60, and define main risk factors. DESIGN--Population based screening study. SETTING--Private Norwegian health maintenance organisation. SUBJECTS--500 men over the age of 60 years. INTERVENTIONS--General examination by a general practitioner, together with measurements of blood glucose and serum cholesterol concentrations. Abdominal scan with a B-mode ultrasound imager. MAIN OUTCOME MEASURES--An increase in the diameter of the aorta of more than 150% over the diameter at the origin of the superior mesenteric artery, or maximum diameter of more than 29 mm. Correlation with history of smoking, serum cholesterol concentration, and general health. RESULTS--29 patients (5.8%) had small, and 12 (2.4%) had large, abdominal aortic aneurysms. There was a significant association between aortic aneurysm and history of smoking (p < 0.01), poor health (defined as coexistent hypertension, cardiovascular disease, or diabetes mellitus) (p < 0.01), and increasing age (p = 0.025). There was no association with hypercholesterolaemia. CONCLUSION--Ultrasonic screening of groups at risk followed by elective operation may reduce mortality of abdominal aortic aneurysm.     

Cost-effectiveness of screening women for abdominal aortic aneurysm

BACKGROUND: Women are usually not considered for abdominal aortic aneurysm (AAA) screening because of their lower prevalence of disease. This position may, however, be questioned given the higher risk of rupture and the longer life expectancy among women. The purpose of this study was to assess the cost-effectiveness of screening 65-year-old women for AAA. METHODS: A systematic review of the literature was conducted to obtain data of importance to evaluate the effectiveness of screening women for AAA. Data were entered into a Markov simulation cohort model. RESULTS: The review suggested some main assumptions for women with AAA. Prevalence is 1.1%. In 6.8%, the AAA is of a size that merits surgery, and the patients are fit for a procedure. For patients with an AAA, the yearly risk for elective surgery and the rupture incidence was 3.1% and 2.4%, respectively, in the invited group and 1.1% and 5.7% in the noninvited group. The operative mortality for elective surgery was 3.5%, and the total mortality for ruptured AAA was 86.3%. The long-term mortality for AAA patients was 3.6 times higher than for an age-matched healthy population. Screening reduced the AAA rupture incidence by 33% and the AAA-related death rate by 35%. The cost per life year gained was estimated at $5911. CONCLUSION: The incremental cost-effectiveness ratio was similar to that found for screening men, which reflects the fact that the lower AAA prevalence in women is balanced by a higher rupture rate. Screening women for AAA may be cost-effective, and future evaluations on screening for AAA should include women.     

The case for expanding abdominal aortic aneurysm screening

Both the U.S. Preventive Services Task Force and the UK National Institute for Health and Care Excellence are re-evaluating their screening paradigms for abdominal aortic aneurysms (AAAs). Currently, most countries that screen for AAA do so only in male ever-smokers between the ages of 65 and 75 years and in patients with a family history of AAA. However, these recommendations are based primarily on screening trials predating the endovascular era. The wider applicability of endovascular aneurysm repair and its safety profile, especially in the elderly, have changed the risk-benefit of repair and, by extension, screening. This is despite the decreasing prevalence of AAA thanks to improved medical therapies and lower smoking rates. This evidence summary critically examines the evidence behind screening and the potential for expanded screening.     

Cost-effectiveness of different screening strategies for abdominal aortic aneurysm

OBJECTIVE: The primary objective of this study was to develop a simulation model to assess the cost-effectiveness of different screening strategies for abdominal aortic aneurysms (AAAs) in men. METHODS: A systematic review of the literature was conducted for different screening strategies in terms of age (60, 65, or 70 years) and risk profiles (all men or specific high-risk groups) of the screened population, and rescreening after 5 or 10 years. These data were analyzed in a Markov simulation cohort model. RESULTS: The cost per life year gained for different screening strategies ranged from US 8,309 dollars to US 14,084 dollars and was estimated at US 10,474 dollars when 65-year-old men were screened once. Screening 60-year-old men was equally cost-effective, with the advantage of more life years gained. We demonstrated a trade-off between high prevalence of AAA and lower life expectancy, eliminating the expected benefits of screening high-risk groups such as smokers (US 10,695 dollars) or cardiovascular patients (US 10,392 dollars). Assuming general population utility resulted in a cost per quality-adjusted life year (QALY) gained of US 13,900 dollars, whereas a hypothetical 5% reduction in utility among men with a screening-detected AAA raised the cost per QALY gained to US 75,100 dollars. CONCLUSION: This Markov model, which was based on a systematic review of the literature, supplied information on the estimated cost-effectiveness of different screening strategies. Screening men for AAA may be cost-effective in the long-term. Different screening strategies and quality-of-life effects related to screening for AAA need to be evaluated in future clinical studies.     

High-risk and low-risk screening for abdominal aortic aneurysm both reduce aneurysm-related mortality. A stratified analysis from a single-centre randomised screening trial.

BACKGROUND: Cardiovascular diseases and chronic obstructive pulmonary disease (COPD) are both associated with abdominal aortic aneurysms (AAA). The aim of this study was therefore to analyse whether screening for AAA could be restricted to men with such diseases (high risk group). METHODS: Before the date of randomisation of a population screening trial of 12,639 64-73-year-old males, all discharge diagnoses from the National Patient Registry concerning AAA-related diseases were merged with the screening results on attendance, AAA prevalence, and AAA-related mortality and overall mortality. Differences in proportions were compared by Chi square tests and differences in mortality by Cox regression analyses. RESULTS: The attendance rate was 78.8% and 6.7% had an AAA in the high risk group compared to 75.8% attendance (P<0.001) and 2.9% (P<0.001) in the remaining population. Cumulatively, screening of only high risk men with would have required 72.9% (95% C.I.: 72.3-74.5%) fewer screening invitations, would have discovered 46.1% (95% C.I.: 38.9-53.4%) of the AAA cases diagnosed and prevented 46.7% (95% C.I.: 28.3-65.7%) of the AAA-related deaths. However, screening decreased AAA-related mortality both among men with and without known COPD or cardiovascular diseases: mortality ratio: 0.22 (95% C.I.: 0.08-0.65), P=0.006, and 0.24 (95% C.I: 0.09-0.63, P=0.004, respectively. CONCLUSION: High-risk population screening would prevent less than half of AAA-related deaths. Therefore, restricting screening to such high-risk groups does not seem justified, but cost effectiveness analyses are needed to reach a firm conclusion.     

Ultrasound screening for abdominal aortic aneurysm in medicare beneficiaries

Ultrasound screening for abdominal aortic aneurysm (AAA) has been shown to be beneficial and cost-effective for men aged 65-74. However, most screening studies have been conducted in Europe and Australia, where attendance for screening was higher than the single large U.S. study involving only veterans. The prevalence of AAA in the U.S. general population is not well defined, nor is the best method of recruitment for screening. Letters of invitation for a free screening ultrasound for AAA were sent to 30,000 randomly selected Medicare beneficiaries from the hospital referral region of three university-affiliated hospitals without restriction by age, gender, or comorbidity. Attendance for screening was calculated by age, gender, and travel distance to the screening center. Telephone calls to a random sample of nonresponders were made to determine the reason for failure to attend. Prevalence of AAA by ultrasound and known risk factors for AAA (e.g., age, gender, smoking status) were determined. The attendance rate was 7% (2,005). Attendance was greater with male gender (p < 0.01), younger age (p < 0.05), and decreased travel distance to the screening center (p < 0.05). The primary reasons for failure to attend included incorrect address or vital status, poor health, and lack of interest. Prevalence of previously undetected AAA was 2.8% in men and 0.2% in women. AAA was predicted by smoking status and male gender (p < 0.01 for each). Unselected invitation of Medicare beneficiaries for ultrasound screening for AAA results in a low attendance and low yield of AAA. The prevalence estimates from this study may not reflect the entire Medicare population given the low attendance and may reflect the healthy habits of those most interested in screening. Patients should be selected for screening based on their suitability for repair if an AAA is found as well as their risk factors for AAA. The best method of recruitment for screening of those most at risk for AAA in the United States remains to be determined.     

Measuring abdominal aortic diameters in routine abdominal computed tomography scans and implications for abdominal aortic aneurysm screening

Objective

This study aimed to determine the prevalence and relevance of incidental abdominal aortic aneurysm (AAA) on routine abdominal computed tomography (CT) and to audit the performance of radiologists to identify and report AAA.