1. A review of one-time ultrasound screening for abdominal aortic aneurysms (AAAs) demonstrated that screening was associated with significantly reduced AAA-related morality in men aged >65 years of age. However, no effect was shown for all-cause morality.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Abdominal aortic aneurysms (AAAs) are often asymptomatic until the development of an acute rupture, which is associated with high mortality rates. Thus, there has been great interest in the role of screening for AAAs. Ultrasound (US) is widely accepted as the standard screening method for abdominal aortic aneurysms (AAAs). In a previous statement, the U.S. Preventative Services Task Force (USPSTF) recommended one-time ultrasound screening for men 65-75 years old who have smoked. This updated systematic review incorporated newly-identified literature on the effectiveness of one-time and repeated US screening for AAA in an asymptomatic population.
The review identified 4 fair to good quality RCTs that included participants aged 65 years or older. All trials showed a trend towards reduction in AAA-related mortality rates in men beginning at 3 months and up to 15 years, though this trend was only significant for only 2 out of 4 of the trials. However, the systematic review did not find a statistically significant reduction in all-cause mortality associated with US screening. In terms of weighing the possible harms of screening, the review did find that screening was associated with more overall surgeries, although rates of emergency operations and 30-day operative mortality were lower. The 1 trial that included women showed no significant effect on AAA-related or all-cause morality for this gender. Overall, this systematic review provides evidence there may be a role for one-time screening with US for reducing AAA-related morbidity and morality.
In-Depth [systematic review]: The investigators considered randomized control trials and large cohort studies of asymptomatic populations for this review. Poor-quality studies were excluded. The authors identified 2 fair quality and 2 good quality population-based screening studies that assessed the efficacy of AAA screening in population based settings. The good quality trials included the MASS (multicenter aneurysm screening study) and the Chinchester, United Kingdom screening trial. The 2 fair quality trials were the Valborg County Denmark screening trial and the western Australian screening trial. All trials used intention to treat analysis, and the primary trial outcome was AAA-specific mortality. AAA prevalence ranged from 4.0-7.7%, and most were small, measuring less than 4.0-4.5cm. The 2 good quality trials showed statistically significant reductions in AAA-related mortality at 3 months and up to 15 years. The fair-quality trials showed a trend towards AAA-related mortality reductions, but these did not reach statistical significance. The individual trials as well as the pooled date analysis did not show any significant reduction in all-cause mortality associated with screening. The Chinchester trial was the only 1 to include women, and this trial did not show any significant effect on AAA-related mortality. The rates of AAA-related surgeries was almost double in all individual trials, although this was driven mostly by elective surgeries (hazard ratio ranged from 1.7-2.4). One trial (MASS) reported on thirty-day postoperative mortality rates. Postoperative mortality rates were significantly reduced after emergency surgery in the screened groups.
By Aimee Li, MD and Andrew Cheung, MD
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