No screening asymptomatic CAS in general population, says USPSTF 

　　2007年12月18日    Michael O’Riordan

　　主题：心脏介入治疗，及预防

　　Rockville（罗克维尔），MD（医务属）－美国预防服务特别小组 （US Preventive Services Task Force, USPSTF）提出有关无症状颈动脉狭窄（carotid artery stenosis，CAS）筛选使用的新临床指南，结论为筛选的“中等程度的肯定”带来的获益不能超过其危险性。由此，特别小组指出，对于无症状的个体应当无需进行人群的常规CAS筛查。

　　2007年12月18日在Annal of Internal Medicine上发表的USPSTF提供的推荐等级为D，参考了Dr Tracy Wolff（Agency for Healthcare Research and Quality， 健康维护研究和品质代理机构，Rockville，MD）及同时的相关证据回顾资料。上一次公布指南是在1996年，特别小组没能够提出充分的依据建议或反对对无症状的CAS患者进行筛查，包括体检和颈动脉超声检查。目前最新的建议是USPSTF根据检查的证据，包括颈动脉狭窄的自然进程，筛查试验的准确性回顾，以及临床试验关于颈动脉内膜剥脱术治疗CAS获益证据的回顾。

　　根据筛查，特别小组指出二维超声是最简便易行的检测手段，但其只有中等程度的敏感性和特异性，并有较多的假阳性结果。阳性结果通常靠造影来确定，该结果更准确，但经常导致严重的负作用或不良事件。无创的确定性监测，如核磁（MRI），也可能不够准确。

　　USPSTF指出：“提供这些事实依据，一些患者的假阳性结果可能会导致接受不必要的有创性颈动脉剥脱术治疗”。
有关监测和早期干预，特别小组提出了很好的依据－来自无症状颈动脉粥样硬化研究（Asymptomatic Carotid Atherosclerosis Study，ACAS ）和无症状颈动脉外科手术试验（Asymptomatic Carotid Surgery Trail，ACST）表明对无症状的严重CAS患者中的高危患者，选择性的颈动脉内膜剥脱手术能绝对降低5年的所有中风发生率或围手术期的死亡率5％。然而，这些获益在整体人群中获益可能很小，而且对于普通一级治疗的患者，“评价获益称度不高于低等级”。
USPSTF的报告没有回顾药物治疗的依据，但是指出选择接受药物治疗策略有助于预防中风。

　　USPSTF的最终结论是：“对人群进行筛选与颈动脉内膜剥脱术治疗之间仍存在证据上的空隙，仍需要研究来提供全面获益的依据，临床医师在医疗实践中应当更多致力于采用适当的药物方法治疗中风的危险因素”。

　　（阜外心血管病医院　杨伟宪　编译）

　　（来源：www.theheart.org）

No screening asymptomatic CAS in general population, says USPSTF 

December 18, 2007 

Michael O’Riordan

Topic: Interventional cardiology, and prevention.

Rockville, MD - The US Preventive Services Task Force (USPSTF) has issued new clinical guidelines regarding the use of screening for asymptomatic carotid artery stenosis (CAS) and concludes with "moderate certainty" that the benefits of screening do not outweigh the risks [1]. With this, the task force concludes that asymptomatic individuals in the general population should not be routinely screened for CAS.

The class D recommendation of the USPSTF is now published in the December 18, 2007 issue of the Annals of Internal Medicine and is based on a review of the evidence by Dr Tracy Wolff (Agency for Healthcare Research and Quality, Rockville, MD) and colleagues [2]. The last guidelines were published in 1996, with the task force concluding then that the evidence was insufficient to recommend for or against screening of asymptomatic patients for CAS by physical examination or carotid ultrasonography. To update this recommendation, the USPSTF examined evidence on the natural history of carotid stenosis and reviewed the accuracy of the screening tests, as well as reviewing clinical-trial evidence of the benefits of treating CAS with carotid endarterectomy.

Regarding screening, the task force writes that while duplex ultrasonography is the most feasible test, it has only moderate sensitivity and specificity and yields many false-positive results. Positive results are usually confirmed by angiography, which is more accurate but also poses risks of serious adverse events. Noninvasive confirmation tests, such as magnetic resonance imaging (MRI), can also be inaccurate.

"Given these facts, some people with false-positive test results may receive unnecessary invasive carotid endarterectomy surgery," according to the USPSTF.

In terms of detection and early intervention, the task force notes that good evidence—from the Asymptomatic Carotid Atherosclerosis Study (ACAS) and the Asymptomatic Carotid Surgery Trial (ACST)—has shown that in high-risk subjects with asymptomatic, severe CAS, carotid endarterectomy by selected surgeons reduces the five-year absolute incidence of all strokes or perioperative death by 5%. However, these benefits, they write, would be less among the general population, and for the general primary-care patient, "the benefits are judged to be no greater than small."

The USPSTF report did not review the evidence on medical treatment but notes that accepted medical strategies to prevent stroke are available.

"Until research addresses the gaps in the evidence that screening and treatment with carotid endarterectomy provides overall benefits to the general population, clinicians’ efforts might be more practically focused on optimizing medical management of risk factors of stroke," concludes the USPSTF.