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作者：Emma Hitt, PhD  
出處：WebMD醫學新聞

　　March 22, 2010 — 包含「嚴重高血壓(severe hypertension[S])、意識混亂(confusion[C])、抗凝血劑(anticoagulation[A])以及噁心嘔吐(nausea and vomiting[N])；簡稱SCAN規則」等四項症狀的規則，在輕微中風病患的顱內出血(intracerebral hemorrhage[ICH])辨識上似乎具有特定性與敏感度。
　　
　　SCAN 規則指出，如果輕微中風病患出現至少一項這四種預測變項，該病患可能會有ICH。相較於已經有ICH或者在治療前需要進一步腦部影像檢查(磁振造影[MRI]或電腦斷層[CT])者，這項規則有助於確認哪些病患可以安全地立即使用抗血小板製劑治療。
　　
　　之前任職於英國牛津John Radcliffe醫院，目前任職於倫敦St. George's醫院醫學中心神經科的Caroline E. Lovelock醫師(MBChB, DPhil, FRACP)與研究夥伴在3月份的神經學、神經外科學與精神醫學期刊(Journal of Neurology, Neurosurgery Psychiatry)中發表他們的研究發現。
　　
　　Lovelock醫師向Medscape Neurology表示，因為CT腦部影像對於發作幾天後的急性出血較不敏感，SCAN規則對於需要優先接受MRI的遲發型病患的辨識特別有用，如此可以使ICH的誤診風險降到最低。
　　
　　研究者試圖藉由334名輕微中風病患(定義為美國國衛院腦中風評估表分數小於等於3分)辨識出與ICH有關的臨床因素，將獲自此一世代的預測模式運用在另一個有280名病患的世代上加以驗證，在最初世代和確認世代中，約5%的病患有ICH。
　　
　　研究作者寫道，在醫院門診確認世代中，約24%病患有至少一種臨床預測因子，但是ICH病患則有93%出現這些因子之一，如果出現兩種以上臨床預測因子，掃描時有25%病患發現ICH的證據。
　　
　　彙整最初世代和確認世代的資料後，SCAN規則偵測ICH的敏感度為97%(95%信心區間[CI]為84% – 99%)、專一度為74%(95% CI，70% – 77%)。
　　
　　【運用於各種健康照護環境】
　　Lovelock醫師表示，使用於遲發型輕微中風病患的SCAN規則，可以運用於美國和英國的健康照護體系，她指出，即使在有高度資源的健康照護體系中，輕微中風病患仍舊較慢受到注意，特別是社會弱勢或地處偏遠者。
　　
　　根據Lovelock醫師表示，SCAN規則也可運用於較貧窮的國家，用來辨識哪些輕微中風病患優先需要接受初步CT檢查來排除ICH，不過，還需要先在其他健康照護環境中進行確認。
　　
　　Lovelock醫師指出，但是，SCAN規則不可以取代腦部影像檢查用來診斷ICH，它只是一種幫助擬定輕微中風患者之適當檢查與治療計畫的指引，用於那些最可能有ICH之患者時的考量。
　　
　　【並非取代腦部影像檢查】
　　根據英國愛丁堡大學Enda Kerr和Rustam Al-Shahi Salman兩位醫師的編輯評論，SCAN規則最有用的貢獻是，它的陰性預測價值達99.8%(95% CI，99% – 100%)。
　　
　　他們指出，對於SCAN分數0分的那70%輕微中風病患，幾乎可以完全排除ICH。
　　
　　但是，雖然SCAN規則可以排除SCAN 分數0分者的ICH，它還不足以取代即時且適當地腦部影像檢查的需要。
　　
　　他們指出，腦部影像檢查可以藉由辨識缺血性中風的血管範圍，以排除出血，排除假性中風、影響預後估計以及處置策略，所以，當有腦部影像檢查設備時，對各個中風案例立即進行腦部掃描依舊是最有成本效益的策略，且可以獲得最大的調整品質後存活人年。
　　
　　Lovelock醫師、Kerr醫師以及Al-Shahi Salman醫師皆宣告沒有相關財務關係，該研究使用的資料來自「Oxford Vascular Study」這項由英國醫學研究委員會、Dunhill醫學信託基金、中風協會、BUPA基金會、國家健康研究中心(NIHR)、Thames Valley Primary Care Research Partnership以及NIHR牛津生醫研究中心等資助的研究。  


SCAN Rule May Reduce Misdiagnosis of ICH in Patients With Minor Stroke

By Emma Hitt, PhD
Medscape Medical News

March 22, 2010 — A rule involving 4 symptoms — severe hypertension (S), confusion (C), anticoagulation (A), and nausea and vomiting (N) — appears to be specific and sensitive at identifying intracerebral hemorrhage (ICH) in patients with minor stroke.

The SCAN rule states that if at least 1 of these 4 predictive variables is present in a patient with minor stroke, the patient is likely to have ICH. The rule may help determine which patients can be safely treated immediately with antiplatelet agents compared with those who might have ICH and would need further brain imaging (magnetic resonance imaging [MRI] or computed tomography [CT]) before treatment.

Caroline E. Lovelock, MBChB, DPhil, FRACP, formerly with the John Radcliffe Hospital in Oxford, United Kingdom, and now with the Department of Neurology at St. George's Hospital Medical School in London, United Kingdom, and colleagues published their findings in the March issue of Journal of Neurology, Neurosurgery Psychiatry.

"Because CT brain imaging becomes insensitive to an acute bleed after only a few days, the SCAN rule is particularly useful for identifying which late-presenting patients need priority access to MRI brain imaging so that the risk of misdiagnosing an ICH can be minimized," Dr. Lovelock told Medscape Neurology.

The researchers sought to identify clinical factors associated with ICH in 334 consecutive patients with minor stroke, defined as a National Institutes of Health Stroke Scale score of 3 or less. The predictive model derived in this cohort was then further validated in a separate cohort of 280 patients. Approximately 5% of patients in the initial and validation cohorts had ICH.

"In the hospital clinic validation cohort, at least 1 clinical predictor was present in 24% of patients but in 93% of patients with ICH," the study authors write. "If 2 or more clinical predictors were present, 25% of patients had evidence of ICH on scan."

Data pooled from the derivation and validation cohorts indicated that the SCAN rule had a sensitivity of 97% (95% confidence interval [CI], 84% – 99%) and a specificity of 74% (95% CI, 70% – 77%) for the detection of ICH.

Utility in Various Healthcare Settings

The SCAN rule, which is applicable to late-presenting patients with minor stroke, should be useful in both the US and UK healthcare systems, Dr. Lovelock said. Even in a highly resourced healthcare system, she noted, "patients with minor stroke may still present late to medical attention, particularly if they are relatively socially or geographically isolated."

According to Dr. Lovelock, the SCAN rule may also be useful in poorer countries, "where it can be used to identify which patients with minor stroke need priority access to early CT imaging to rule out ICH," although it still requires validation in different healthcare settings.

Dr. Lovelock noted, though, that the SCAN rule should not be used as an alternative to brain imaging to diagnose ICH. "Instead it is a guide to help plan appropriate investigations and treatment for patients with minor stroke, in whom the possibility of an underlying ICH always needs to be considered."

Not an Alternative to Brain Imaging

According to a related editorial by Enda Kerr and Rustam Al-Shahi Salman with the University of Edinburgh, United Kingdom, "the most useful attribute of the SCAN rule might be its negative predictive value of 99.8% (95% CI, 99% – 100%).

"For the 70% of patients with minor stroke who had a SCAN score of zero, ICH was almost completely ruled out," they point out.

Still, although the SCAN rule almost "rules out ICH in patients with minor strokes and a SCAN score of zero, it is insufficient to completely refute the need for timely and appropriate brain imaging."

Brain imaging can also do more than exclude hemorrhage by identifying the vascular territory of an ischemic stroke, ruling out stroke "mimics" and potentially influencing prognosis estimates or management strategies, they add. "So, where brain imaging facilities permit, immediate brain scanning for all strokes remains the policy that is most cost-effective and results in the greatest gain in quality-adjusted life-years."

Dr. Lovelock, Dr. Kerr, and Dr. Al-Shahi Salman have disclosed no relevant financial relationships. The study used data from the Oxford Vascular Study, which is funded by the UK Medical Research Council, the Dunhill Medical Trust, the Stroke Association, the BUPA Foundation, the National Institute for Health Research (NIHR), the Thames Valley Primary Care Research Partnership, and the NIHR Oxford Biomedical Research Centre.

J Neurol Neurosurg Psychiatry. 2010;81:271-275, 239.