Background: The U.S. Federal Government enacted the Screen for Abdominal Aortic Aneurysms Very Efficiently Act in January 2007. Simultaneously, the Department of Veterans Affairs (VA) implemented a more inclusive AAA screening policy for veteran beneficiaries shortly afterwards.
Our study aimed to evaluate the impact of the VA program on AAA detection rate and all-cause mortality compared to a cohort of patients whose aneurysms were identified by other abdominal imaging.
Methods: We identified veterans with an AAA screening study using the two existing Current Procedural Terminology (CPT) codes (G0389 and 76706). In the comparison group, eligible abdominal imaging studies included ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI) queried according to CPT codes between 2001 and 2018.
We used a difference-in-differences regression model to evaluate the change in aneurysm detection rate and all-cause mortality five years before and eleven years after the VA implemented the screening policy in 2007.
We calculated survival estimates after AAA screening or non-screening imaging of patients with or without AAA diagnosis and used multivariate Cox regression model to evaluate mortality in patients with a positive AAA diagnosis adjusting for patient characteristics and comorbidities.
Results: We identified 3.9 million veterans with abdominal imaging, a total of 303,664 of whom were coded has having an AAA US screening between 2007 and 2018. An AAA diagnosis was made in 4.84% of the screening group vs. 1.3% in the non-screening imaging group P<0.001, yet more aneurysms were found with general imaging studies (50,730 vs.15,449) (Fig 1).
On Kaplan-Meier survival analysis, patients with an AAA diagnosis had higher overall mortality than patients who screened normal; patients with aneurysms found with non-screening imaging had the highest mortality, log-rank P<0.001 (Fig 2).
The difference in differences regression analysis, showed that the absolute AAA detection rate was 1.55% higher (95% CI 1.2- 1.8), and the mortality was 13.89 % lower (95% CI 10.18 %-16.66 %) after the introduction of the screening program in 2007.
Multivariate Cox regression analysis in patients with AAA diagnosis (65-74-year-old) demonstrated a significantly lower 5-year mortality [HR 0.45 (95% CI 0.43-0.48)] for patients in the US Screening group P<0.001.
Conclusions: In a nationwide analysis of VA patients, implementation of AAA screening was associated with improved survival and a higher rate of AAA diagnosis. These findings provide further support for this program's continuation versus defaulting to incidental recognition following other abdominal imaging.