Kabrhel Christopher, Mark Courtney D, Camargo Carlos A, Moore Christopher L, Richman Peter B, Plewa Michael C, Nordenholtz Kristen E, Smithline Howard A, Beam Daren M, Brown Michael D, Kline Jeffrey A
Department of Emergency Services, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
Acad Emerg Med. 2009 Apr;16(4):325-32. doi: 10.1111/j.1553-2712.2009.00368.x. Epub 2009 Mar 6.
The utility of D-dimer testing for suspected pulmonary embolism (PE) can be limited by test specificity. The authors tested if the threshold of the quantitative D-dimer can be varied according to pretest probability (PTP) of PE to increase specificity while maintaining a negative predictive value (NPV) of >99%.
This was a prospective, observational multicenter study of emergency department (ED) patients in the United States. Eligible patients had a diagnostic study ordered to evaluate possible PE. PTP was determined by the clinician's unstructured estimate and the Wells score. Five different D-dimer assays were used. D-dimer test performance was measured using 1) standard thresholds and 2) variable threshold values: twice (for low PTP patients), equal (intermediate PTP patients), or half (high PTP patients) of standard threshold. Venous thromboembolism (VTE) within 45 days required positive imaging plus decision to treat.
The authors enrolled 7,940 patients tested for PE, and clinicians ordered a quantitative D-dimer for 4,357 (55%) patients who had PTPs distributed as follows: low (74%), moderate (21%), or high (4%). At standard cutoffs, across all PTP strata, quantitative D-dimer testing had a test sensitivity of 94% (95% confidence interval [CI] = 91% to 97%), specificity of 58% (95% CI = 56% to 60%), and NPV of 99.5% (95% CI = 99.1% to 99.7%). If variable cutoffs had been used the overall sensitivity would have been 88% (95% CI = 83% to 92%), specificity 75% (95% CI = 74% to 76%), and NPV 99.1% (95% CI = 98.7% to 99.4%).
This large multicenter observational sample demonstrates that emergency medicine clinicians currently order a D-dimer in the majority of patients tested for PE, including a large proportion with intermediate PTP and high PTP. Varying the D-dimer's cutoff according to PTP can increase specificity with no measurable decrease in NPV.
D - 二聚体检测用于疑似肺栓塞（PE）时，其效用可能受检测特异性限制。作者测试了定量D - 二聚体的阈值是否可根据PE的预测试概率（PTP）进行调整，以提高特异性，同时保持阴性预测值（NPV）>99%。
这是一项针对美国急诊科（ED）患者的前瞻性观察性多中心研究。符合条件的患者接受了用于评估可能的PE的诊断性检查。PTP由临床医生的非结构化估计和Wells评分确定。使用了五种不同的D - 二聚体检测方法。D - 二聚体检测性能通过以下方式衡量：1）标准阈值；2）可变阈值：标准阈值的两倍（低PTP患者）、相同（中等PTP患者）或一半（高PTP患者）。45天内的静脉血栓栓塞（VTE）需要影像学检查阳性并决定治疗。
作者纳入了7940例接受PE检测的患者，临床医生为4357例（55%）患者开具了定量D - 二聚体检测，这些患者的PTP分布如下：低（74%）、中（21%）或高（4%）。在标准临界值下，在所有PTP分层中，定量D - 二聚体检测的敏感度为94%（95%置信区间[CI]=91%至97%），特异性为58%（95%CI = 56%至60%），NPV为99.5%（95%CI = 99.1%至99.7%）。如果使用可变临界值，总体敏感度将为88%（95%CI = 83%至92%），特异性为75%（95%CI = 74%至76%），NPV为99.1%（95%CI = 98.7%至99.4%）。
这个大型多中心观察样本表明，急诊医学临床医生目前在大多数接受PE检测的患者中开具了D - 二聚体检测，包括很大比例的中等PTP和高PTP患者。根据PTP改变D - 二聚体的临界值可提高特异性，且NPV无明显下降。
