Mass screening on abdominal aortic aneurysm in men aged 60 to 65 years in The Netherlands. Impact on life expectancy and cost-effectiveness using a Markov model

Health gains, costs and cost-effectiveness of a population-based screening programme for abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) rupture carries a high fatality rate. AAAs can be detected before rupture by abdominal ultrasound imaging, allowing elective repair. Population-based screening for AAA in older men reduces AAA-related mortality by about 40 per cent. The UK began an AAA screening programme offering one-off scans to men aged 65 years in 2009. Sweden has a similar programme. Currently, there is no AAA screening programme in New Zealand. This cost-utility analysis aimed to assess the cost-effectiveness of a UK-style screening programme in the New Zealand setting.

METHODS

The analysis compared a formal AAA screening programme (one-off abdominal ultrasound imaging for about 20 000 men aged 65 years in 2011) with no systematic screening. A Markov macrosimulation model was adapted to estimate the health gains (in quality-adjusted life-years, QALYs), health system costs and cost-effectiveness in New Zealand. A health system perspective and lifetime horizon was adopted.

RESULTS

With New Zealand-specific inputs, the adapted model produced an estimate of about NZ $15 300 (€7746) per QALY gained, with a 95 per cent uncertainty interval (UI) of NZ $8700 to 31 000 (€4405 to 15 694) per QALY gained. Health gains were estimated at 117 (95 per cent UI 53 to 212) QALYs. Health system costs were NZ $1·68 million (€850 535), with a 95 per cent UI of NZ $820 200 to 3·24 million (€415 243 to €1·65 million).

CONCLUSION

Using New Zealand's gross domestic product per capita (about NZ $45 000 or €22 100) as a cost-effectiveness threshold, a UK-style AAA screening programme would be cost-effective in New Zealand.

APC-PCI complex levels for screening of AAA in patients with peripheral atherosclerosis

To evaluate the use of activated protein C-protein C inhibitor (APC-PCI) complex levels for detection of abdominal aortic aneurysm (AAA) in patients with peripheral atherosclerotic disease (PAD). APC-PCI levels and aortic diameter evaluated in 511 PAD patients without previously known AAA followed-up concerning survival for 4.8(0.5) years. AAA was found in 13% of patients. Aortic diameter correlated (r = 0.138; p = 0.002) with APC-PCI levels which were higher (0.40[0.45] vs. 0.30[0.49] μg/l; p = 0.004) in patients with AAA. This difference persisted in multivariate analysis (p = 0.029). A threshold value of APC-PCI ≥0.15 μg/L showed a specificity of 11%, a sensitivity of 97% and a negative predictive value of 96% for an AAA diagnosis. APC-PCI levels were higher in patients with AAA, and showed high sensitivity but low specificity for the diagnosis and can therefore not be considered as a screening tool in PAD patients. An AAA prevalence of 13% in patients with PAD indicates a need for AAA screening within this population.

Prevalence and trends of the abdominal aortic aneurysms epidemic in general population--a meta-analysis

OBJECTIVE

To conduct a meta-analysis assessing the prevalence and trends of the abdominal aortic aneurysms (AAA) epidemic in general population.

METHOD

Studies that reported prevalence rates of AAA from the general population were identified through MEDLINE, EMBASE, Web of Science, and reference lists for the period between 1988 and 2013. Studies were included if they reported prevalence rates of AAA in general population from the community. In stratified analyses possible sources of bias, including areas difference, age, gender and diameter of aneurysms were examined. Publication bias was assessed with Egger's test method.

RESULTS

56 studies were identified. The overall pooled prevalence of AAA was 4.8% (4.3%, 5.3%). Stratified analyses showed the following results, areas difference: America 2.2% (2.2%, 2.2%), Europe 2.5% (2.4%, 2.5%), Australia 6.7% (6.5%, 7.0%), Asia 0.5% (0.3%, 0.7%); gender difference: male 6.0% (5.3%, 6.7%), female 1.6% (1.2%, 1.9%); age difference: 55-64years 1.3% (1.2%, 1.5%), 65-74 years 2.8% (2.7%, 2.9%), 75-84 years1.2%(1.1%, 1.3%), ≥85years0.6% (0.4%, 0.7%); aortic diameters difference: 30-39 mm, 3.3% (2.8%, 3.9%), 40-49 mm,0.7% (0.4%,1.0%), ≥50 mm, 0.4% (0.3%, 0.5%). The prevalence of AAA has decreased in Europe from 1988 to 2013. Hypertension, smoking, coronary artery disease, dyslipidemia, respiratory disease, cerebrovascular disease, claudication and renal insufficiency were risk factors for AAA in Europe.

CONCLUSION

AAA is common in general population. The prevalence of AAA is higher in Australia than America and Europe. The pooled prevalence in western countries is higher than the Asia. Future research requires a larger database on the epidemiology of AAA in general population.

Analysis of cost effectiveness of screening Danish men aged 65 for abdominal aortic aneurysm

OBJECTIVE

To assess the cost effectiveness of screening men aged 65 for abdominal aortic aneurysm.

DESIGN

Cost effectiveness analysis based on a probabilistic, enhanced economic decision analytical model from screening to death.

POPULATION AND SETTING

Hypothetical population of men aged 65 invited (or not invited) for ultrasound screening in the Danish healthcare system.

DATA SOURCES

Published results from randomised trials and observational epidemiological studies retrieved from electronic bibliographic databases, and supplementary data obtained from the Danish Vascular Registry.

DATA SYNTHESIS

A hybrid decision tree and Markov model was developed to simulate the short term and long term effects of screening for abdominal aortic aneurysm compared with no systematic screening on clinical and cost effectiveness outcomes. Probabilistic sensitivity analyses using Monte Carlo simulation were carried out. Results were presented in a cost effectiveness acceptability curve, an expected value of perfect information curve, and a curve showing the expected (net) number of avoided deaths from abdominal aortic aneurysm over time after the introduction of screening. The model was validated by calibrating base case health outcomes and expected activity levels against evidence from the recent Cochrane review of screening for abdominal aortic aneurysm.

RESULTS

The estimated costs per quality adjusted life year (QALY) gained discounted at 3% per year over a lifetime for costs and QALYs was pound43 485 (euro54,852; $71,160). At a willingness to pay threshold of pound30,000 the probability of screening for abdominal aortic aneurysm being cost effective was less than 30%. One way sensitivity analyses showed the incremental cost effectiveness ratio varying from pound32,640 to pound66,001 per QALY.

CONCLUSION

Screening for abdominal aortic aneurysm does not seem to be cost effective. Further research is needed on long term quality of life outcomes and costs.

Screening for abdominal aortic aneurysm in asymptomatic at-risk patients using emergency ultrasound

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a deadly but often clinically silent disease. Patients at increased risk are elderly men with risk factors for vascular disease who may not have adequate screening through primary care. We sought to examine the prevalence and feasibility of screening for AAA in at-risk patients presenting for unrelated complaints using emergency physician-performed bedside ultrasound.

METHODS

At-risk patients presenting with unrelated complaints were screened for AAA by emergency physician-performed ultrasound. Scan was rated as complete, limited, or inadequate, and time to complete scan noted. Patients with identified AAA were provided with appropriate follow-up and were followed to look at confirmatory imaging and clinical course.

RESULTS

A total of 179 patients were screened, with 12 AAAs discovered (6.7%; 95% confidence interval, 3.9%-11.4%). Average time to perform the screening ultrasound was 141 +/- 135 seconds. Average discrepancy between emergency ultrasound and formal imaging was 3.9 mm. Of 12 (92%) patients, 11 were followed up, with repair recommended in 3 patients.

CONCLUSION

The emergency department represents a potential opportunity for screening at-risk patients for AAA. Emergency ultrasound is a fast and accurate method for identifying patients with AAA who may benefit from follow-up or intervention.

Is population screening for abdominal aortic aneurysm cost-effective?

BACKGROUND

Ruptured abdominal aortic aneurysm (AAA) is responsible for 1-2% of all male deaths over the age of 65 years. Early detection of AAA and elective surgery can reduce the mortality risk associated with AAA. However, many patients will not be diagnosed with AAA and have therefore an increased death risk due to the untreated AAA. It has been suggested that population screening for AAA in elderly males is effective and cost-effective. The purpose of this study was to perform a systematic review of published cost-effectiveness analyses of screening elderly men for AAA.

METHODS

We performed a systematic search for economic evaluations in NHSEED, EconLit, Medline, Cochrane, Embase, Cinahl and two Scandinavian HTA data bases (DACEHTA and SBU). All identified studies were read in full and each study was systematically assessed according to international guidelines for critical assessment of economic evaluations in health care.

RESULTS

The search identified 16 cost-effectiveness studies. Most studies considered only short term cost consequences. The studies seemed to employ a number of "optimistic" assumptions in favour of AAA screening, and included only few sensitivity analyses that assessed less optimistic assumptions.

CONCLUSION

Further analyses of cost-effectiveness of AAA screening are recommended.

Screening for Abdominal Aortic Aneurysms in Cardiovascular Patients

BACKGROUND

The objective of the study was to determine the incidence of Abdominal Aortic Aneurysms (AAA) in a population of symptomatic cardiac patients. A retrospective cohort study of investigations was done at the cardiology clinic, Beaumont Hospital, Dublin.

MATERIALS AND METHODS

There were 415 men and women recruited by referral to the cardiology clinic. All participants underwent routine ultrasound screening for AAA, and full assessment of all cardiac risk factors. Data were analyzed and correlated with age, sex, and diagnosis.

RESULTS

Ultrasonographic diagnosis of aneurysm was based on an anteroposterior diameter of 3 cm or more. Of the 415 patients screened, 47 aneurysms were detected. Total incidence of AAA was 9.9% (male 14.1%, female 3.95%). All aneurysms were detected in patients over 60 years, detection rate 11.7% (male 16.3%, female 3.9%). The incidence of AAA was significantly higher in those who were subsequently proven to have cardiovascular disease, 13.8% (male 18%, female 5.15%).

CONCLUSION

Screening the general population for those at risk of AAA is an ongoing debate. This study supports the concept of screening a higher risk population of patients over 60 years with cardiovascular disease.

Growth Rate and Associated Factors in Small Abdominal Aortic Aneurysms

OBJECTIVE

To study the growth rate and factors influencing progression of small infrarenal abdominal aortic aneurysms (AAA).

DESIGN

Observational, longitudinal, prospective study.

PATIENTS AND METHODS

We followed patients with AAA <5 cm in diameter in two groups. Group I (AAA 3-3.9 cm, n = 246) underwent annual ultrasound scans. Group II (AAA 4-4.9 cm, n = 106) underwent 6-monthly CT scans.

RESULTS

We included 352 patients (333 men and 19 women) followed for a mean of 55.2+/-37.4 months (6.3-199.8). The mean growth rate was significantly greater in group II (4.72+/-5.93 vs. 2.07+/-3.23 mm/year; p<0.0001). Group II had a greater percentage of patients with rapid aneurysm expansion (>4 mm/year) (36.8 vs. 13.8%; p<0.0001). The classical cardiovascular risk factors did not influence the AAA growth rate in group I. Chronic limb ischemia was associated with slower expansion (< or = 4 mm/year) (OR 0.47; CI 95% 0.22-0.99; p = 0.045). Diabetic patients in group II had a significantly smaller mean AAA growth rate than non-diabetics (1.69+/-3.51 vs. 5.22+/-6.11 mm/year; p = 0.032).

CONCLUSIONS

The expansion rate of small AAA increases with the AAA size. AAA with a diameter of 3-3.9 cm expand slowly, and they are very unlikely to require surgical repair in 5 years. Many 4-4.9 cm AAA can be expected to reach a surgical size in the first 2 years of follow-up. Chronic limb ischemia and diabetes are associated with reduced aneurysm growth rates.

Detection of Abdominal Aortic Aneurysm in Patients with Peripheral Artery Disease

OBJECTIVE

To describe the prevalence of abdominal aortic aneurysms (AAA) in patients with peripheral artery disease (PAD).

DESIGN

Observational, descriptive, transverse study.

PATIENTS AND METHODS

We performed an abdominal ultrasound in 1190 consecutive patients with lower limb chronic ischemia (1/99-12/04). We registered cardiovascular risk factors and clinical data for analysis.

RESULTS

The ultrasound was inconclusive in 24 (2%) patients; 1166 patients completed the study. They were mostly male (93.7%), with an age mean of 67+/-9.9 years (37.7-93.4). The main cardiovascular risk factors were: smoking (80.9%), hypertension (41.7%) and hypercholesterolemia (31.4%). The prevalence of AAA was 13% (n = 151). Only 1.5% (n = 17) of the patients had a large AAA (>5 cm). The AAA was clearly more prevalent in men (n = 148; 13.6%) than in women (n = 3; 4.1%) (RR 3.47; 95% CI 1.11-10.89; p = 0.02). The prevalence significantly increased with age, with a maximum of 17.1% in over 75-year-old men (p = 0.006). Patients with tibial disease had a significantly higher prevalence of AAA than aortoiliac or femoro-popliteal disease (p = 0.02).

CONCLUSIONS

The prevalence of AAA in patients with PAD is much higher than that reported in the general population. We recommend that an abdominal ultrasound be routinely included in the study of these patients. Over 75-year-old men are at particularly high-risk.

Abdominal aortic aneurysm (AAA): cost-effectiveness of screening, surveillance of intermediate-sized AAA, and management of symptomatic AAA

Physicians must make decisions about screening patients for abdominal aortic aneurysms (AAAs), monitoring or referring for surgery patients with AAAs of various sizes, and assessing patients with symptoms that may be related to AAAs. This review article analyzes the evidence for each scenario. The effectiveness and cost-effectiveness of screening for AAA is based on results from four randomized controlled trials. A cost-effectiveness analysis using a Markov model showed that ultrasound screening of white men beginning at age 65 is both effective and cost-effective in preventing AAA-related death. Such screening would have a small but real impact over a 20-year period in these men. For patients with a known AAA-which is often detected incidentally-the evidence clearly suggests periodic ultrasound surveillance for those with small AAAs (3.0-3.9 cm in diameter) and elective surgical repair for those with large AAAs (>or=5.5 cm). Two recent randomized controlled trials have shown that early surgical repair confers no survival benefit compared with periodic surveillance for patients with intermediate-sized AAAs (4.0-5.5 cm in diameter), so those patients can also be monitored. Some centers choose to increase the frequency of monitoring to every 3 to 6 months when the AAA reaches 5.0 cm. Factors to consider in assessing symptomatic patients include the high risk of life-threatening conditions, the potential increased risk of death or poor outcome with delay in diagnosis, the limitations of ultrasound in identifying whether symptoms are due to known or suspected AAA, and the timely availability of computed tomography or other imaging tests. If available, computed tomography is preferred in patients with recent or severe symptoms, since it is better at detecting retroperitoneal hemorrhage and other complications and in providing preoperative definition of the anatomy.

Abdominal aortic aneurysm screening during transthoracic echocardiography in an unselected population

OBJECTIVE

We sought to investigate the echocardiographic prevalence of abdominal aortic aneurysm (AAA) in an unselected group of patients referred for regular transthoracic echocardiography (TTE).

METHODS

Prospectively, during a 3-month period, a limited ultrasound examination of the infrarenal aorta was performed. AAA was defined as a diameter of 30 mm or more.

RESULTS

The abdominal aorta could be visualized in 742 patients. The prevalence of AAA was 4.6%. AAA prevalence increased with age, especially in men. In 34 patients AAA was unknown and aortic diameters exceeded 50 mm in 4 patients. Two underwent elective but urgent operation. Patients with AAA were older and had an increased ascending aorta diameter, larger left ventricular dimensions, higher left ventricular mass index, and lower ejection fraction.

CONCLUSION

AAA is prevalent in patients referred for regular TTE. Routine rapid screening of the abdominal aorta during TTE is beneficial and should, therefore, be part of a standard TTE examination for patients older then 50 years.

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.