Centre for Population Health Sciences, University of Edinburgh, Scotland.
JAMA. 2010 Mar 3;303(9):841-8. doi: 10.1001/jama.2010.221.
A low ankle brachial index (ABI) indicates atherosclerosis and an increased risk of cardiovascular and cerebrovascular events. Screening for a low ABI can identify an asymptomatic higher risk group potentially amenable to preventive treatments.
To determine the effectiveness of aspirin in preventing events in people with a low ABI identified on screening the general population.
DESIGN, SETTING, AND PARTICIPANTS: The Aspirin for Asymptomatic Atherosclerosis trial was an intention-to-treat double-blind randomized controlled trial conducted from April 1998 to October 2008, involving 28,980 men and women aged 50 to 75 years living in central Scotland, free of clinical cardiovascular disease, recruited from a community health registry, and had an ABI screening test. Of those, 3350 with a low ABI (< or = 0.95) were entered into the trial, which was powered to detect a 25% proportional risk reduction in events.
Once daily 100 mg aspirin (enteric coated) or placebo.
The primary end point was a composite of initial fatal or nonfatal coronary event or stroke or revascularization. Two secondary end points were (1) all initial vascular events defined as a composite of a primary end point event or angina, intermittent claudication, or transient ischemic attack; and (2) all-cause mortality.
After a mean (SD) follow-up of 8.2 (1.6) years, 357 participants had a primary end point event (13.5 per 1000 person-years, 95% confidence interval [CI], 12.2-15.0). No statistically significant difference was found between groups (13.7 events per 1000 person-years in the aspirin group vs 13.3 in the placebo group; hazard ratio [HR], 1.03; 95% CI, 0.84-1.27). A vascular event comprising the secondary end point occurred in 578 participants (22.8 per 1000 person-years; 95% CI, 21.0-24.8) and no statistically significant difference between groups (22.8 events per 1000 person-years in the aspirin group vs 22.9 in the placebo group; HR, 1.00; 95% CI, 0.85-1.17). There was no significant difference in all-cause mortality between groups (176 vs 186 deaths, respectively; HR, 0.95; 95% CI, 0.77-1.16). An initial event of major hemorrhage requiring admission to hospital occurred in 34 participants (2.5 per 1000 person-years) in the aspirin group and 20 (1.5 per 1000 person-years) in the placebo group (HR, 1.71; 95% CI, 0.99-2.97).
Among participants without clinical cardiovascular disease, identified with a low ABI based on screening a general population, the administration of aspirin compared with placebo did not result in a significant reduction in vascular events.
isrctn.org Identifier: ISRCTN66587262.
低踝臂指数（ABI）表明存在动脉粥样硬化和心血管及脑血管事件风险增加。通过筛查低 ABI 可以发现无症状的高危人群，这些人群可能适合接受预防性治疗。
确定在一般人群筛查中发现低 ABI 的人群中，阿司匹林在预防事件中的有效性。
设计、地点和参与者：阿司匹林用于无症状动脉粥样硬化试验（Aspirin for Asymptomatic Atherosclerosis trial）是一项意向治疗、双盲、随机对照试验，于 1998 年 4 月至 2008 年 10 月进行，涉及年龄在 50 至 75 岁之间、居住在苏格兰中部、无临床心血管疾病的 28980 名男性和女性，他们从社区健康登记处招募而来，并且进行了 ABI 筛查测试。其中，ABI 较低（≤0.95）的 3350 人进入试验，试验有能力检测到事件风险降低 25%的比例。
每天一次服用 100 毫克阿司匹林（肠溶）或安慰剂。
主要终点是初始致命或非致命性冠状动脉事件或中风或血运重建的复合终点。两个次要终点是：（1）所有初始血管事件，定义为主要终点事件或心绞痛、间歇性跛行或短暂性脑缺血发作的复合终点；（2）全因死亡率。
平均（标准差）随访 8.2（1.6）年后，357 名参与者发生了主要终点事件（每 1000 人年 13.5 例，95%置信区间[CI]，12.2-15.0）。两组之间未发现统计学上的显著差异（阿司匹林组每 1000 人年 13.7 例，安慰剂组每 1000 人年 13.3 例；危险比[HR]，1.03；95%CI，0.84-1.27）。包含次要终点的血管事件发生在 578 名参与者中（每 1000 人年 22.8 例；95%CI，21.0-24.8），两组之间也没有统计学上的显著差异（阿司匹林组每 1000 人年 22.8 例，安慰剂组每 1000 人年 22.9 例；HR，1.00；95%CI，0.85-1.17）。两组之间的全因死亡率也没有显著差异（分别为 176 例和 186 例死亡；HR，0.95；95%CI，0.77-1.16）。阿司匹林组有 34 名（每 1000 人年 2.5 例）和安慰剂组有 20 名（每 1000 人年 1.5 例）参与者发生了需要住院治疗的大出血初始事件（HR，1.71；95%CI，0.99-2.97）。
在没有临床心血管疾病的参与者中，根据一般人群的筛查发现低 ABI 后，与安慰剂相比，阿司匹林治疗并未显著降低血管事件的发生。
isrctn.org 标识符：ISRCTN66587262。
