Strategies to improve the effectiveness of abdominal aortic aneurysm screening programmes

Cost-effectiveness of a population-based AAA screening program for men over 65 years old in Iran

BACKGROUND

Screening program tend to recognized patients in their early stage and consequently improve health outcomes. Cost-effectiveness of the abdominal aortic aneurysm (AAA) screening program has been scarcely studied in developing countries. We sought to evaluate the cost-effectiveness of a screening program for the abdominal aortic aneurysm (AAA) in men aged over 65 years in Iran.

METHODS

A Markov cohort model with 11 mutually exclusive health statuses was used to evaluate the cost-effectiveness of a population-based AAA screening program compared with a no-screening strategy. Transitions between the health statuses were simulated by using 3-month cycles. Data for disease transition probabilities and quality of life outcomes were obtained from published literature, and costs were calculated based on the price of medical services in Iran and the examination of the patients' medical records. The outcomes were life-years gained, the quality-adjusted life-year (QALY), costs, and the incremental cost-effectiveness ratio (ICER). The analysis was conducted for a lifetime horizon from the payer's perspective. Costs and effects were discounted at an annual rate of 3%. Uncertainty surrounding the model inputs was tested with deterministic and probabilistic sensitivity analyses.

RESULTS

The mean incremental cost of the AAA screening strategy compared with the no-screening strategy was $140 and the mean incremental QALY gain was 0.025 QALY, resulting in an ICER of $5566 ($14,656 PPP) per QALY gained. At a willingness-to-pay of 1 gross domestic product (GDP) per capita ($5628) per QALY gained, the probability of the cost-effectiveness of AAA screening was about 50%. However, at a willingness-to-pay of twice the GDP per capita per QALY gained, there was about a 95% probability for the AAA screening program to be cost-effective in Iran.

CONCLUSIONS

The results of this study showed that at a willingness-to-pay of 1 GDP per capita per QALY gained, a 1-time AAA screening program for men aged over 65 years could not be cost-effective. Nevertheless, at a willingness-to-pay of twice the GDP per capita per QALY gained, the AAA screening program could be cost-effective in Iran. Further, AAA screening in high-risk groups could be cost-effective at a willingness-to-pay of 1 GDP per capita per QALY gained.

ANG II infusion promotes abdominal aortic aneurysms independent of increased blood pressure in hypercholesterolemic mice

Infusion of ANG II in hyperlipidemic mice augments atherosclerosis and causes formation of abdominal aortic aneurysms (AAAs). The purpose of this study was to define the contribution of ANG II-induced hypertension to these vascular pathologies. Male apolipoprotein E (apoE)- and LDL receptor (LDLr)-deficient mice were infused with ANG II (1,000 ng.kg(-1).min(-1)) or norepinephrine (NE; 5.6 mg.kg(-1).day(-1)) for 28 days. Infusion of ANG II or NE increased mean arterial pressure (MAP; ANG II, 133 +/- 2.8; NE, 129 +/- 13 mmHg) to a similar extent compared with baseline blood pressures (MAP, 107 +/- 2 mmHg). Abdominal aortic width increased in both apoE-deficient (apoE(-/-)) or LDLr-deficient (LDLr(-/-)) mice infused with ANG II (apoE(-/-): 1.4 +/- 0.1; LDLr(-/-): 1.6 +/- 0.2 mm). In contrast, NE did not change diameters of abdominal aortas (apoE(-/-): 0.91 +/- 0.03; LDLr(-/-): 0.87 +/- 0.02 mm). Similarly, atherosclerotic lesions in aortic arches were much greater in mice infused with ANG II compared with NE. At a subpressor infusion rate of ANG II (500 ng.kg(-1).min(-1)), AAAs developed in 50% of apoE(-/-) mice. Alternatively, administration of hydralazine (250 mg/l) to ANG II-infused apoE(-/-) mice (1,000 ng.kg(-1).min(-1)) lowered systolic blood pressure (day 28: ANG II, 157 +/- 6; ANG II/hydralazine, 135 +/- 6 mmHg) but did not prevent AAA formation or atherosclerosis. These results demonstrate that infusion of ANG II to hyperlipidemic mice induces AAAs and augments atherosclerosis independent of increased blood pressure.

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.

A Comparison Between the Short Term and Long Term Benefits of Screening for Abdominal Aortic Aneurysms from the Huntingdon Aneurysm Screening Programme

BACKGROUND

The UK Multicentre Aneurysm Screening Study (MASS) showed a 44% reduction in AAA-related mortality after 4 years and predicted an increased number of deaths prevented in the longer term. We aim to compare the 5 and 13 years benefit from aneurysm screening in the Huntingdon Aneurysm screening programme.

METHODS

Incidence and mortality of ruptured AAA (RAAA) after 5 and 13 years of screening in a population based aneurysm screening program.

RESULTS

Five years of screening resulted in a reduction in the incidence of RAAA of 49% (95% CI: 3-74%). Nine out of 11 ruptures in the invited group did not survive (mortality 82%; 95% CI: 48-98%) compared to 38 non-survivors from 51 ruptures in the control group (mortality 75%; 95% CI: 60-86%). Five years of screening resulted in an RAAA-related mortality reduction of 45% (95% CI: -15 to 74%). After 13 years of screening the incidence of RAAA was reduced by 73% (95% CI: 58-82%). Twenty-one out of 29 ruptures in the invited group did not survive (mortality 72%; 95% CI: 53-87%) compared to 64 non-survivors from 82 ruptures in the control group (mortality 78%; 95% CI: 68-86%). Thirteen years screening resulted in a reduction of mortality from RAAA of 75% (95% CI: 58-84%). The number needed to screen to prevent one death reduced from 1380 after 5 years to 505 after 13 years. The number of elective AAA operations needed to prevent one death reduced from 6 after 5 years to 4 after 13 years.

CONCLUSION

AAA screening becomes increasingly beneficial as screening continues over the longer term. Benefits continue to increase after screening has ceased.