Whitty C J, Sudlow C L, Warlow C P
Department of Clinical Sciences, London School of Hygiene and Tropical Medicine, UK.
J Neurol Neurosurg Psychiatry. 1998 May;64(5):619-23. doi: 10.1136/jnnp.64.5.619.
Trials suggesting that carotid endarterectomy in individual subjects with asymptomatic carotid stenosis reduces stroke risk have led to calls for screening. This study aimed to determine which groups might be harmed and which might benefit from a screening programme, and also to identify which individual subjects identified as positive for severe asymptomatic stenosis by carotid ultrasound are appropriate to put forward for further tests or procedures.
A probability model was used to estimate the outcomes of three screening strategies: carotid ultrasound followed by catheter angiography, or by magnetic resonance angiography (MRA), or ultrasound alone, followed by carotid endarterectomy if severe stenosis is detected. Information from the current literature was used to estimate sensitivity and specificity of ultrasound and MRA, risks of angiography and endarterectomy, and risk reduction after surgery for severe stenosis. For each strategy over a range of possible prevalences of severe asymptomatic stenosis, overall benefit to harm ratio was calculated, and number of strokes or deaths prevented or caused per 10,000 subjects screened.
At the prevalence of carotid stenosis found in the general population (<1%) screening will cause more strokes than it prevents, even using the most optimistic published figures. Only at prevalences of over 20% are significant benefits seen, and then only in centres with high test sensitivity and specificity and very low angiographic and surgical risk. Groups with such a high prevalence have not yet been reliably identified. Screening individual subjects from high prevalence groups would have limited public health impact, with at best about 100 strokes prevented for every 10,000 screened at 20% prevalence.
Investigating asymptomatic individual subjects for carotid stenosis may be harmful except in high prevalence groups. There is insufficient information about which these groups are, and at present screening cannot be recommended. Acting on a positive carotid ultrasound test in individual subjects
试验表明，对无症状性颈动脉狭窄的个体进行颈动脉内膜切除术可降低中风风险，这引发了筛查的呼声。本研究旨在确定哪些群体可能会受到伤害，哪些群体可能从筛查计划中受益，同时确定通过颈动脉超声被确定为严重无症状狭窄阳性的个体中，哪些适合进一步检查或进行手术。
使用概率模型估计三种筛查策略的结果：先进行颈动脉超声检查，然后进行导管血管造影或磁共振血管造影（MRA），或者仅进行超声检查，如果检测到严重狭窄则进行颈动脉内膜切除术。利用当前文献中的信息估计超声和MRA的敏感性和特异性、血管造影和内膜切除术的风险，以及严重狭窄手术后的风险降低情况。对于一系列可能的严重无症状狭窄患病率的每种策略，计算总体利弊比，以及每10000名接受筛查的受试者预防或导致的中风或死亡人数。
在一般人群中发现的颈动脉狭窄患病率（<1%）下，即使使用已发表的最乐观数据，筛查导致的中风也会多于预防的中风。只有在患病率超过20%时才会看到显著益处，而且只有在检测敏感性和特异性高、血管造影和手术风险非常低的中心才会如此。尚未可靠地确定具有如此高患病率的群体。对高患病率群体中的个体进行筛查对公共卫生的影响有限，在患病率为20%时，每10000名接受筛查的人中最多可预防约100例中风。
对无症状个体进行颈动脉狭窄检查可能有害，除非是在高患病率群体中。目前关于哪些是这些群体的信息不足，因此目前不建议进行筛查。对个体的颈动脉超声检查阳性结果采取行动
