Hammer Mark M, Litt Harold I
Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
Am J Emerg Med. 2016 Oct;34(10):1968-1972. doi: 10.1016/j.ajem.2016.07.002. Epub 2016 Jul 4.
With increasing utilization of computed tomography pulmonary angiography (CTPA) for the diagnosis of pulmonary embolism (PE), many patients undergo repeat CTs.
The aim of this study is to identify the rate of positive subsequent CTPAs after an initial negative CTPA and whether there is a risk-free period after a negative CTPA.
We evaluated 318 patients with at least 1 subsequent CTPA after an initial negative CTPA, with 786 total CTPAs. We also evaluated a control group of 200 unselected CTPAs.
The positive rate in the repeat group was 7% at the first repeat CTPA and 10% per-patient within 1000 days. The positive rate in the control group was 9% (P= not significant). No risk-free period was seen, with a positive rate of 5% within 2 weeks after a negative CTPA. The number of prior negative CTPAs showed a trend towards decreasing rate of the subsequent CTPA being positive, but this did not meet statistical significance.
There is no risk-free period after an initial negative CTPA, and therefore, patients with clinical suspicion of PE should be rescanned even after a recent negative study. Even patients with multiple negative prior CTPAs have a measurable risk of subsequent PE. Established clinical prediction scoring systems must be used to triage the patients who need CTPAs.
随着计算机断层扫描肺动脉造影（CTPA）在肺栓塞（PE）诊断中的应用日益增加，许多患者接受了重复CT检查。
本研究的目的是确定初次CTPA结果为阴性后，后续CTPA结果为阳性的比例，以及阴性CTPA后是否存在无风险期。
我们评估了318例初次CTPA结果为阴性后至少接受1次后续CTPA检查的患者，共进行了786次CTPA检查。我们还评估了一个由200例未经过筛选的CTPA检查组成的对照组。
重复检查组在首次重复CTPA时的阳性率为7%，在1000天内每位患者的阳性率为10%。对照组的阳性率为9%（P=无显著性差异）。未观察到无风险期，阴性CTPA后2周内的阳性率为5%。既往阴性CTPA的次数显示出后续CTPA结果为阳性的比例有下降趋势，但未达到统计学显著性。
初次CTPA结果为阴性后不存在无风险期，因此，即使近期检查结果为阴性，临床怀疑PE的患者也应再次进行扫描。即使既往有多次阴性CTPA结果的患者，后续发生PE的风险也是可测量的。必须使用既定的临床预测评分系统对需要进行CTPA检查的患者进行分类。
