Evaluation of a quantitative D-dimer latex immunoassay for acute pulmonary embolism diagnosed by computed tomographic angiography

OBJECTIVE: To determine the sensitivity and specificity of a quantitative plasma fibrin D-dimer latex immunoassay (LIA) for the diagnosis of acute pulmonary embolism. SUBJECTS AND METHODS: Study subjects were Mayo Clinic Rochester inpatients and outpatients with suspected acute pulmonary embolism; all had undergone quantitative D-dimer LIA testing and multidetector-row computed tomographic (CT) angiography between August 3, 2001, and November 10, 2003. Multidetector-row CT angiography was the diagnostic reference standard. RESULTS: Of 1355 CT studies, 208 (15%) were positive for acute pulmonary embolism. Median D-dimer levels were significantly higher for patients with acute pulmonary embolism (1425 ng/mL) than for patients without (500 ng/mL) (P<.001). The highest specificity that optimizes sensitivity for acute pulmonary embolism was achieved by using a discriminant value of 300 ng/mL, which yielded a sensitivity of 0.94 (95% confidence interval [CI], 0.89-0.97), a specificity of 0.27 (95% CI, 0.25-0.30), and a negative predictive value of 0.96 (95% CI, 0.93-0.98). CONCLUSION: The quantitative D-dimer LIA with a discriminant value of 300 ng/mL had high sensitivity and high negative predictive value but low specificity for the diagnosis of acute pulmonary embolism. On the basis of these results, we believe that a negative quantitative D-dimer LIA result and a low pretest probability of thromboembolism together are sufficient to exclude acute pulmonary embolism.     

Sensitivity and specificity of the semiquantitative latex agglutination D-dimer assay for the diagnosis of acute pulmonary embolism as defined by computed tomographic angiography

OBJECTIVE: To determine the sensitivity and specificity of the semiquantitative latex agglutination plasma fibrin D-dimer assay for the diagnosis of acute pulmonary embolism by using computed tomographic (CT) angiography as the diagnostic reference standard. PATIENTS AND METHODS: From January 1, 1998, to June 26, 2000, patients who had both semiquantitative latex agglutination plasma fibrin D-dimer testing and CT angiography for suspected acute pulmonary embolism were selected for the study. A D-dimer value greater than 250 ng/mL was considered positive for thromboembolic disease. Diagnosis of acute pulmonary embolism was based solely on the interpretation of the CT angiogram. The D-dimer assay results were then compared with the CT angiographic diagnoses. RESULTS: Of 946 CT studies, 172 (18%) were positive for acute pulmonary embolism. The D-dimer assay was positive for 612 (65%) of the 946 patients. For acute pulmonary embolism, the D-dimer assay had a sensitivity of 0.83 (95% confidence interval [CI], 0.76-0.88), a specificity of 039 (95% CI, 036-0.43), a negative likelihood ratio of 0.44 (95 % CI, 032-0.62), and a negative predictive value of 0.91 (95% CI, 0.87-0.94). CONCLUSIONS: The semiquantitative latex agglutination plasma fibrin D-dimer assay had moderate sensitivity and low specificity for the diagnosis of acute pulmonary embolism. When used alone, the results of this test were insufficient to exclude this serious and potentially fatal disorder. Approximately two thirds of our patients had positive D-dimer assays and required further evaluation to exclude acute pulmonary embolism.     

Clinical probability and alveolar dead space measurement for suspected pulmonary embolism in patients with an abnormal D-dimer test result

BACKGROUND: Most patients with suspected pulmonary embolism (PE) have a positive D-dimer test and undergo diagnostic imaging. Additional non-invasive bedside tests are required to reduce the need for further diagnostic tests. OBJECTIVES: We aimed to determine whether a combination of clinical probability assessment and alveolar dead space fraction measurement can confirm or exclude PE in patients with an abnormal D-dimer test. METHODS: We assessed clinical probability of PE and alveolar dead space fraction in 270 consecutive in- and outpatients with suspected PE and positive D-dimer. An alveolar dead space fraction < 0.15 was considered normal. PE was subsequently excluded or confirmed by venous compression ultrasonography, spiral computed tomography and a 3-month follow-up. Radiologists were unaware of the results of clinical probability and capnography. RESULTS: PE was confirmed in 108 patients (40%). Capnography had a sensitivity of 68.5% (95% confidence interval [CI]: 58.9-77.1%) and a specificity of 81.5% (95% CI: 74.6-87.1%) for PE. Forty-five patients (16.6%) had both a low clinical probability and normal capnography (sensitivity: 99.1%, 95% CI: 94.9-100%) and 34 patients (12.6%) had both a high clinical probability and abnormal capnography (specificity: 100%, 95% CI: 97.7-100%). CONCLUSION: Capnography alone does not exclude PE accurately. The combination of clinical probability and capnography accurately excludes or confirms PE and avoids further testing in up to 30% of patients.     

血浆D-二聚体对疑似肺栓塞患者诊断价值的研究

目的：探讨血浆 D-二聚体对对疑似肺栓塞患者的诊断价值。方法采用自动化免疫比浊法测定患者血浆D-二聚体水平。统计分析血浆D-二聚体诊断肺栓塞的敏感性、特异性、阴性及阳性预测值,并绘制ROC曲线以评价其诊断价值并对D-二聚体阴性排除肺栓塞价值进行分析。结果在317例疑似肺栓塞患者中D-二聚体＜500μg/L的患者73例,其中6例被诊断为肺栓塞。D-二聚体对肺栓塞的诊断的敏感性为95.86%（95%CI：91.27%～98.08%）,特异性为38.95%（95%CI：31.98%～41.41%）,阴性预测值为91.78%（95%CI：83.21%～96.18%）,阳性预测值为56.97%（95%CI：50.69%～63.02%）,诊断准确性为64.98%（95%CI：59.58%～70.03%）。ROC曲线下面积为0.674（95%CI：0.615～0.733）。结论 D-二聚体对肺栓塞的诊断具有较高的敏感性,阴性排除肺栓塞的准确性较高,但仍可受患者年龄、测试方法等的影响。     

增强与非增强MR肺动脉血管成像诊断肺栓塞准确性的对比研究

目的比较对比增强MR血管成像(contrast-enhanced MR pulmonary angiography,CE-MRA)与非增强空间标记多反转脉冲序列(applying spatial labeling with multiple inversion pulses sequence,SLEEK)MR血管成像诊断肺栓塞(pulmonary embolism,PE)的准确性。材料与方法 26例CT肺动脉血管成像诊断肺栓塞的患者(男15例,女11例)于多排螺旋CT肺动脉造影(CT pulmonary angiography,CTPA)检查48 h内行CE-MRA以及非增强SLEEK MR检查。CTPA作为参考标准,计算并比较每种MR技术诊断肺栓塞的敏感性、特异性、阳性预测值以及阴性预测值。结果 CE-MRA诊断肺栓塞的敏感性为78.8%,特异性97.7%。非增强SLEEK MRI诊断肺栓塞的敏感性83.8%,特异性100%。两阅片者间存在高度一致性(k=0.87)。结论 CE-MRA和SLEEK MRI诊断肺栓塞的准确性无统计学差异,但非增强SLEEK MRI血管成像无需使用对比剂,有希望成为肺栓塞诊断策略中的一部分。     

An Emergency Department Guideline for the Diagnosis of Pulmonary Embolism: An Outcome Study

OBJECTIVE: To assess the clinical outcome of patients suspected of pulmonary embolism (PE) following implementation of an emergency department (ED) diagnostic guideline. METHODS: A prospective observational study of all patients suspected of PE who presented to the ED during a four-month study period. The authors' modification of the Charlotte criteria recommended D-dimer testing in those younger than 70 years of age with a low clinical suspicion of PE and no unexplained hypoxemia, unilateral leg swelling, recent surgery, hemoptysis, pregnancy, or prolonged duration of symptoms. The primary outcome was the identification of venous thromboembolism during a three-month follow-up period. The negative predictive value of the overall diagnostic strategy and the test characteristics of D-dimer were calculated. RESULTS: A total of 1,207 consecutive patients were evaluated for suspected PE; 71 (5.8%) were diagnosed with venous thromboembolism. One missed case of PE was identified on follow-up, yielding a negative predictive value of 99.9% (95% confidence interval [CI] = 99.5% to 100%). The missed case was a patient who presented with pleuritic chest pain and shortness of breath; a chest radiograph revealed pneumothorax, and the physician decided not to pursue the positive D-dimer result. The patient returned six weeks later with PE. Subgroup analysis of patients having D-dimer performed (n = 677) yields a sensitivity of 0.93 (95% CI = 0.77 to 0.98) and a specificity of 0.74 (95% CI = 0.70 to 0.77). CONCLUSIONS: Implementation of a PE diagnostic guideline in a community ED setting is safe and has improved the specificity of the enzyme-linked immunosorbent assay D-dimer test when compared with previous studies.     

D-Dimer test in cancer patients with suspected acute pulmonary embolism

BACKGROUND: The safety of a D-dimer (DD) measurement in cancer patients with clinically suspected pulmonary embolism (PE) is unclear. OBJECTIVES: The aim of this study was to assess the accuracy of the DD test in consecutive patients with clinically suspected PE with and without cancer. METHODS: The diagnostic accuracy of DD (Tinaquant D-dimer) was first retrospectively assessed in an unselected group of patients referred for suspected PE (n = 350). Subsequently, the predictive value of the DD was validated in a group of consecutive inpatients and outpatients with clinically suspected PE prospectively enrolled in a management study (n = 519). The results of the DD test in cancer patients were assessed according to the final diagnosis of PE and the 3-month clinical follow-up. RESULTS: In the first study group, DD showed a sensitivity and a negative predictive value (NPV) of 100% and 100% in patients with cancer and 97% and 98% in those without malignancy, respectively. In the validation cohort, the sensitivity and NPV of DD were both 100% (95% CI 82%-100% and 72%-100%, respectively), whereas in patients without malignancy, the corresponding estimates were 93% (95% CI 87%-98%) and 97% (95% CI, 95%-99%), respectively. The specificity of DD was low in patients with (21%) and without cancer (53%). CONCLUSIONS: A negative DD result safely excludes the diagnosis of PE in patients with cancer. Because of the low specificity, when testing 100 patients with suspected PE, a normal DD concentration safely excludes PE in 15 patients with cancer and in 43 patients without cancer.     

Computed tomography pulmonary angiography in the diagnosis of acute pulmonary embolism in the emergency department

This study was undertaken to evaluate the use of computed tomography pulmonary angiography (CTPA) in patients with pulmonary embolism (PE) who were followed in the emergency department (ED). The files and computer records of 850 patients older than 16 years of age who were seen in the Hacettepe University Hospital ED between April 10, 2001, and December 1, 2005, and who required CTPA for PE prediagnosis and/or another diagnosis, were studied retrospectively. PE was identified by CTPA in 9.4% of 416 women and in 5.8% of 434 men. A significant difference (P< .05) was noted in the women and men in whom PE was detected. The mean age of the patients was 58.13±17.88 y (range, 16–100 y). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for clinical susceptibility to PE among patients who underwent CTPA were assessed at 95.3%, 48.2%, 13%, and 99.2%, respectively. CTPA was done for different reasons: aortic aneurysm dissection (n=1), cough distinctive diagnosis (n=1), dyspnea distinctive diagnosis (n=6), chest pain distinctive diagnosis (n=3), PE prediagnosis (n=51), and other reasons (n=2). Also, sensitivity, specificity, PPV, and NPV were found to be 95.4%, 16.2%, 14.4%, and 96%, respectively, for D-dimer. CTPA, which is accessible on a 24-h basis in the ED, is a valuable tool for the diagnosis of PE.     

Pulmonary embolism and COVID-19: A comparative analysis of different diagnostic models performance

ObjectivePulmonary embolism (PE) is a common complication of SARS-CoV-2 infection. Several diagnostic prediction rules based on pretest probability and D-dimer have been validated in non-COVID patients, but it remains unclear if they can be safely applied in COVID-19 patients. We aimed to compare the diagnostic accuracy of the standard approach based on Wells and Geneva scores combined with a standard D-dimer cut-off of 500 ng/mL with three alternative strategies (age-adjusted, YEARS and PEGeD algorithms) in COVID-19 patients.MethodsThis retrospective study included all COVID-19 patients admitted to the Emergency Department (ED) who underwent computed tomography pulmonary angiography (CTPA) due to PE suspicion. The diagnostic prediction rules for PE were compared between patients with and without PE.ResultsWe included 300 patients and PE was confirmed in 15%. No differences were found regarding comorbidities, traditional risk factors for PE and signs and symptoms between patients with and without PE. Wells and Geneva scores showed no predictive value for PE occurrence, whether a standard or an age-adjusted cut-off was considered. YEARS and PEGeD algorithms were associated with increased specificity (19% CTPA reduction) but raising non-diagnosed PE. Despite elevated in all patients, those with PE had higher D-dimer levels. However, incrementing thresholds to select patients for CTPA was also associated with a substantial decrease in sensitivity.ConclusionNone of the diagnostic prediction rules are reliable predictors of PE in COVID-19. Our data favour the use of a D-dimer threshold of 500 ng/mL, considering that higher thresholds increase specificity but limits this strategy as a screening test.     

The impact of using different age-adjusted cutoffs of D-dimer in the diagnosis of pulmonary thromboembolism

BackgroundThis study was conducted to evaluate the relationship of age-adjusted D-dimer value with different coefficients in diagnosis of pulmonary embolism (PE) in geriatric patients.MethodsThe emergency admissions of the patients aged 65 and over with suspected PE during 2018 were reviewed retrospectively. The demographic characteristics, laboratory tests and radiologic findings of computed tomography pulmonary angiogram (CTPA) or single photon emission computed tomography ventilation/perfusion scintigraphy (V/Q) were recorded. The characteristics of the patients with PE were statistically compared with the patients without PE. The specificity and sensitivity for higher cut-off levels (age × 10–15) were presented.ResultsPE was detected in 39.2% (n = 246) of 628 patients aged 65 years and older included in the study. The multivariate analysis revealed that higher D-dimer level (OR = 1,00011; p < 0.001) and BUN level (OR = 1.025; p = 0.013) were independent risk factors for PE diagnosis in elderly patients. Diagnostic statistics for D-dimer cut-off levels selected from ROC analysis and calculated values as 10–15 times of age showed that if the D-dimer cut-off value used is chosen higher, lower sensitivity rates are obtained. Our results also indicated that the patients with malignancy, renal failure, central PE on CTPA and PE with high probability on SPECT VQ were presented with higher D-dimer values.ConclusionOur results do not support the use of higher D-dimer cut-off levels such as 15 times the age in geriatric population. The impact of the location of PE and comorbidities on the outcomes of these patients must be clarified for determining cut-offs with higher specificity.     

Chinese multi-center study of lung scintigraphy and CT pulmonary angiography for the diagnosis of pulmonary embolism

To evaluate diagnostic value of the PISA-PED and PIOPED II criteria for lung scintigraphy and compare it with CT pulmonary angiography (CTPA) for the detection of pulmonary embolism (PE). Five hundred and forty-four consecutive patients with suspected PE were enrolled. All patients underwent lung ventilation/perfusion (V/P) scan, chest radiography, and CTPA. Two readers used the PIOPED II criteria, and 2 used the PISA-PED criteria for the interpretation of lung scintigraphy. CTPA scans were interpreted by two experienced radiologists. Lung scintigraphy and CTPA were categorized as PE present, absent or non-diagnostic. PE was present in 321 of 544 patients. Using PIOPED II criteria, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 85.1, 82.5, 88.1, and 78.4% respectively for V/P scan. Using PISA-PED criteria, sensitivity, specificity, PPV, and NPV were 86.0, 81.2, 86.8, and 80.1% respectively, and none was non-diagnostic. Sensitivity, specificity, PPV, and NPV were 81.7, 93.4, 94.9, and 77.3%, respectively for CTPA. PISA-PED interpretation has similar diagnostic accuracy to PIOPED II interpretation, does not have non-diagnostic scan, with lower cost and radiation, thus should be considered as a choice for patients with suspected PE.     

D-二聚体在急性主动脉夹层中的诊断价值

目的 探讨血浆D-二聚体水平在急性主动脉夹层(acute aortic dissection,AAD)早期诊断中的价值.方法 选取2006年1月至2009年3月因胸痛就诊于复旦大学中山医院患者共80例,其中40例经动脉三维CT血管成像(CTA)检查确诊为急性主动脉夹层病例作为ADD组,同期以类似症状就诊但最终排除急性主动脉夹层的40例为对照组,所有患者胸痛发生12 h内检测血浆 D-二聚体,比较ADD组与对照组血浆 D-二聚体水平,分析D-二聚体诊断急性主动脉夹层的敏感性、特异性、阳性预测值、阴性预测值,并绘制D-二聚体诊断急性主动脉夹层的受试者工作曲线(receiver operating char-acteristic curve,ROC曲线).所有数据用SPSS 11.5统计软件分析处理,计量资料采用均数±标准差(χ±s)表示,两组间均数比较采用Mann-Whitney检验,以P<0.05为差异具有统计学意义.结果 ADD组血浆在D-二聚体水平明显高于对照组[(5.48±7.95)vs.(0.64±0.75),P<0.01];D-二聚体(>0.5 μg/mL)诊断急性主动脉夹层的敏感性、特异性、阳性预测值和阴性预测值分别为87.5%,62.5%,70%和83.3%,受试者工作曲线下面积为0.848±0.042,95%CI为0.766-0.930.结论 D-二聚体可作为急性主动脉夹层早期诊断有效的筛选指标.     

Outcomes of high pretest probability patients undergoing d-dimer testing for pulmonary embolism: a pilot study

ELISA (enzyme-linked immunosorbent assay) D-dimer testing is commonly used in the evaluation of possible pulmonary embolism (PE) in the emergency department, but is not recommended in high pretest probability patients. Whether a negative ELISA D-dimer can safely rule out PE in these patients is not known, as there have been no large studies comparing ELISA D-dimer results and outcomes in high pretest probability patients. This was a prospective observational pilot study of emergency department patients evaluated for PE. Patients evaluated for PE had pretest probability assessed by the Wells PE Score. High pretest probability was defined as: dichotomized Wells Score > 4 points and patients with trichotomized Wells Score > 6 points. Patients had an ELISA D-dimer ordered by the treating physician. Pulmonary embolism was defined as: positive computed tomography scan, high probability ventilation/perfusion scan, positive pulmonary angiogram, or PE on 3-month follow-up. We calculated sensitivity, specificity, positive and negative predictive value, and likelihood ratios for the ELISA D-dimer. We prospectively enrolled 541 patients who underwent D-dimer testing for PE, of whom 130 patients had Wells Score > 4 and 33 patients had Wells Score > 6 (not mutually exclusive). Of subjects with Wells Score > 4, 23 (18%) were diagnosed with PE and 40 (31%) had a negative D-dimer. No patient with Wells Score > 4 (sensitivity 100%, 95% confidence interval [CI] 82%–100%; specificity 37%, 95% CI 28%–47%) or Wells Score > 6 (sensitivity 100%, 95% CI 63%–100%; specificity 56%, 95% CI 35%–76%) who had a negative D-dimer was diagnosed with PE. The likelihood ratio for a negative D-dimer was 0 for both the Wells > 4, and Wells > 6 groups, however, the upper limits of the confidence interval around the post-test probability for PE were 16% and 33%, respectively, for these high probability groups. In this pilot study, the rapid ELISA D-dimer had high sensitivity and negative predictive value even when applied to patients with high pretest probability for PE. However, with the post-test probability of PE still as high as 16–33% in the negative D-dimer groups, this precludes applying the results to patient care at present. Further testing is warranted to determine whether these findings can be safely incorporated into practice.     

The use of D-dimer testing and Wells score in patients with high probability for acute pulmonary embolism

Rationale, aims and objective  To investigate if a combination of Wells pre-test probability score and D-dimer testing could be used as a safe base for making clinical decisions on further investigations for patients with intermediate to high risks of pulmonary embolism (PE).
Methods  One hundred and twenty patients with signs or symptoms of acute PE were investigated with pulmonary angiography (PA) or contrast enhanced computed tomography of the pulmonary arteries (CTPA), D-dimer testing (Tinaquant^®) and clinical scoring using the Wells pre-test probability score during their first 48 hours at the hospital. Patients were recruited consecutively from emergency departments at two teaching hospitals.
Results  The cut-off value of 0.5 mg L⁻¹ in D-dimer analysis is proved adequate with a negative predictive value (NPV) of 92% in this group of patients with intermediate to high risks. The combination of D-dimer testing and Wells score increases the NPV to 94%. The specificities of both tests were low.
Conclusion  D-dimer and Wells pre-test probability scores are safe to rule out acute PE even in patients with at least an intermediate risk of PE, but the specificity is low. D-dimer testing had a higher NPV than Wells score and the combination improved the algorithm further. The cut-off level for a high risk of PE measured with the Wells score was four and it seems reasonable to use that cut-off level in future algorithms. In addition, both PA and CTPA can present false positive and negative results difficult to interpret.     

Multislice computed tomographic pulmonary angiography for diagnosing pulmonary embolism in the emergency department: has the 'one-stop shop' arrived?

Current diagnostic pathways for pulmonary embolism are complex and involve multiple tests. Clinicians await a single diagnostic modality that accurately rules in or out pulmonary embolism and also provides additional diagnostic and prognostic information. Multislice computed tomographic pulmonary angiography (msCTPA) might be that test. msCTPA has good outcomes using current reference standards and can be used as a stand alone test in low risk patients. Additional leg vein imaging should still be performed for higher-risk patients. CT venography performed immediately after msCTPA has sufficient sensitivity and specificity for proximal deep venous thrombosis to allow a single scan to rule out venous thromboembolism in most patients. Up to 40% of patients have important alternative diagnoses seen on msCTPA. Right ventricular measurements may be calculated from msCTPA data and provide prognostic information for patients with severe PE. This may replace the need for echocardiography in the future. msCTPA provides a safe single radiological investigation for diagnosing PE for most patients, after risk stratification and D-dimer testing. A pathway is provided for msCTPA use in the management of PE in the ED.     

双能量CT肺动脉造影中Lung Vessels软件诊断肺动脉栓塞

目的 评价双能量CT肺动脉造影(DE-CTPA)中采用Lung Vessels软件诊断肺动脉栓塞(PE)的价值。方法 收集接受DE-CTPA扫描的可疑PE患者49例,采用Lung Vessels软件处理图像,记录病变血管的位置及数目,以CTPA结合临床作为诊断PE的金标准,按患者、段动脉及亚段动脉为单位计算Lung Vessels诊断PE的敏感度、特异度、阳性预测值及阴性预测值。结果 CTPA诊断PE患者29例,栓塞动脉共188支,包括段动脉138支,亚段动脉50支。分别以患者、段动脉及亚段动脉为单位,Lung Vessels诊断PE敏感度、特异度、阳性预测值、阴性预测值为96.55%(28/29)、45.00%(9/20)、71.79%(28/39)、90.00%(9/10),65.94%(91/138)、80.38%(598/744)、38.40%(91/237)、92.71%(598/645)和64.00%(32/50)、92.24%(1581/1714)、19.39%(32/165)、98.87%(1581/1599)。结论 DE-CTPA中采用Lung Vessels软件可直观显示肺血管,有助于提高对PE、尤其是段及亚段PE的诊断效能,具有潜在应用前景。     

螺旋CT血管造影对肺栓塞的临床诊断价值

目的前瞻性评价螺旋CT血管造影对临床疑诊为肺栓塞的诊断价值。方法对32例临床疑诊为肺栓塞的患者行螺旋CT血管造影(SCTA)及二维或三维重建,所有患者经多种影像检查方法和/或临床治疗随访证实。SCTA扫描参数取层厚3.0,螺距(pitch)1.5,用SmartPrep软件对比剂智能触发技术获得最佳延迟扫描时间。结果32例临床疑诊肺栓塞中,21例肺栓塞共累及肺动脉105支;SCTA确诊了19例,2例5个亚段肺动脉的栓子漏诊。在11例肺栓塞阴性中,SCTA对10例作出了正确诊断:2例肺癌,4例肺炎,1例夹层动脉瘤,3例未见明显异常;另外1例肺动脉肉瘤,SCTA误诊为肺栓塞。SCTA诊断肺栓塞的特异性90.9%,敏感性90.5%,准确性90.6,阳性预测值95.0%,阴性预测值83.3%。结论螺旋CT血管造影无创、快速、敏感性及特异性高,可作为诊断肺栓塞的首选检查方法。     

Management of suspected pulmonary embolism (PE) by D-dimer and multi-slice computed tomography in outpatients: an outcome study

OBJECTIVES: A prospective outcome study designed to evaluate a simple strategy for the management of outpatients with suspected pulmonary embolism (PE), based on clinical probability, D-dimer, and multi-slice computed tomography (MSCT). METHODS: A cohort of 432 consecutive patients admitted to the emergency department with suspected PE was managed by sequential non-invasive testing. Patients in whom PE was ruled out were not given anticoagulants, but were followed-up for 3 months. RESULTS: Normal D-dimer and low-intermediate clinical probability ruled out PE in 103 patients [24% (95% CI 20-28)]. Seventeen patients had normal D-dimer, but high clinical probability and proceeded to MSCT. All patients proved negative for PE. A total of 329 (76%) patients underwent MSCT examination. Pulmonary embolism was diagnosed in 93 patients [21.5% (95% CI 18-26)] and was ruled out by negative MSCT in 221 patients [51% (95% CI 46-56)]. MSCT scans were determined as inconclusive in 15 (4.5%) patients. No patient developed objectively verified venous thromboembolism (VTE) during the 3-month follow-up period. However, the cause of death was adjudicated as possibly related to PE in two patients, resulting in an overall 3-month VTE risk of 0.6% (95% CI 0-2.2%). The diagnostic algorithm yielded a definite diagnosis in 96.5% of the patients. CONCLUSIONS: This simple and non-invasive strategy combining clinical probability, D-dimer, and MSCT for the management of outpatients with suspected PE appears to be safe and effective.     

Exclusion of pulmonary embolism using quantitative plasma D-dimer assays

Recent quantitative studies using pulmonary angiography as reference method have indicated that the overall accuracy of quantitative D-dimer assays for the exclusion of pulmonary embolism (PE) in patients suspected of PE is poorer than was reported in earlier studies in which the same D-dimer assays were used (90-94% vs 98-100%). An explanation can be found in the fact that the earlier studies are hampered by the fact that the reference method was a compilation of clinical data and non-invasive diagnostic tests rather than a true gold standard. Furthermore, in those studies no discrimination was made between the milder cases of subsegmental PE and the more severe cases of segmental and larger PE. The lack of a true gold standard and preselection leading to reduced proportions of cases of subsegmental PE in the earlier studies rather than differences in the storage conditions of plasma samples or treatment with heparin, appear to have caused the discrepancies in the reported accuracy of D-dimer assays. It is concluded that the sensitivity and negative predictive values obtained with different quantitative D-dimer assays are in close agreement with each other, that is poor for subsegmental PE and excellent for segmental and larger PE. In diagnostic algorithms D-dimer can reliably exclude acute segmental and/or massive PE. Further work-up within 48 hours is still necessary in negative D-dimer outcomes to exclude subsegmental PE.     

Accuracy of single-detector spiral CT in the diagnosis of pulmonary embolism: a prospective multicenter cohort study of consecutive patients with abnormal perfusion scintigraphy.

BACKGROUND: Spiral computed tomography (CT) has emerged as a potentially conclusive diagnostic test to exclude pulmonary embolism (PE) in patients with non-high probability scintigraphy and is already widely used-sometimes as the sole primary diagnostic test in the diagnosis of suspected PE. Its true sensitivity and specificity has, however, not been evaluated previously in a large cohort of consecutive patients. METHODS: In a multicenter prospective study 627 consecutive patients with clinically suspected PE were studied. Patients with normal perfusion scintigraphy were excluded from further analysis. Single-detector spiral CT scanning and ventilation scintigraphy were then performed in all patients to diagnose PE, while pulmonary angiography was performed as the gold standard. The only exceptions were those patients who had both a high-probability VQ scan and a CT scan positive for PE: these patients were considered to have PE and did not undergo additional pulmonary angiography. All imaging tests were read by independent expert panels. RESULTS: Five hundred and seventeen patients were available for complete analysis. The prevalence of PE was 32%. Spiral CT correctly identified 88 of 128 patients with PE, and 92 of 109 patients without PE, for a sensitivity and specificity of 69%[95% confidence interval (CI) 63-75] and 84% (95% CI 80-89), respectively. The sensitivity of spiral CT was 86% (95% CI 80-92) for segmental or larger PE and 21% (95% CI 14-29) in the group of patients with subsegmental PE. CONCLUSION: The overall sensitivity of spiral CT for PE is too low to endorse its use as the sole test to exclude PE. This holds true even if one limits the discussion to patients with larger PE in segmental or larger pulmonary artery branches. We conclude that, in patients with clinically suspected PE and an abnormal perfusion scintigraphy, single-slice detector spiral CT is not sensitive enough to be used as the sole test to exclude PE.