by Frank J. Criado, MD, FACS, FSVM
At CX 2017, we heard the first podium presentation from the SWAN (Screening Women for Abdominal aNeurysms) project. Simon Thompson (Cambridge, UK) presented the information, and he said, “We did not find any combination of screening options for women that would make population-based abdominal aortic aneurysm (AAA) screening cost-effective.”
The NHS Abdominal Aortic Screening Program (NAAASP) for men aged 65 years was initiated in 2009 to reduce deaths from aneurysm rupture and has now been rolled out across the UK. There is no systematic screening for women, since abdominal aortic aneurysm prevalence is substantially lower in women than in men. Also, elective surgery outcomes are worse. “Whether screening should be extended to women is uncertain and SWAN was undertaken to shed light on whether women should be screened,” Thompson said.
It is important to keep in mind that 1/3 of deaths from AAA in the UK are now in women. Modeling of NAAASP showed that the program for men would be cost-effective down to an aneurysm prevalence of 0.35%.
The investigators in the project developed a clinically realistic simulation model of screening, surveillance, and elective and emergency abdominal aortic repair operations. The participant base-case settings were for women aged 65 years, followed up to age 95, who were invited to ultrasound screening, followed by surveillance for small AAA and elective repair for large aneurysms.
The main outcome measures of the project were the number of operations undertaken; aneurysm-related mortality; quality-adjusted life-years; and NHS costs and cost-effectiveness with annual discounting. The base-case results for women showed that following invitation to screening, elective operations would rise by 21%; emergency operations would fall by 6%; and deaths from AAA would go down by 4%. Furthermore, per 100,000 women invited to screening, there would be 207 years-of-life gained and £3.54m additional costs. The cost-effectiveness was calculated as £45,000 per quality-adjusted life-year (QALY) gained, and the UK guideline for acceptance in the NHS is <£20,000 per QALY.
“In the absence of randomized trial data, detailed modelling is the best approach. However, some parameters are very uncertain in women and poorly estimated, potentially lacking relevance or are unavailable for women,” Thompson cautioned while discussing the limitations of the study.