Use of spiral computed tomography contrast angiography and ultrasonography to exclude the diagnosis of pulmonary embolism in the emergency department

Spiral computed tomography (CT) contrast angiography is a promising imaging modality for the diagnosis of pulmonary embolism but the negative predictive value of this test remains controversial. We performed a multi-center prospective cohort study to determine the safety of relying on a negative spiral CT contrast angiography scan to exclude pulmonary embolism. Patients presenting to the Emergency Departments of three tertiary care institutions with clinically suspected pulmonary embolism were potentially eligible for the study. Patients underwent a clinical evaluation to categorize pretest probability into low, moderate, and high categories, and had D-dimer testing performed. Patients at low pretest probability with normal D-dimer were considered to have pulmonary embolism excluded. The remaining patients underwent spiral CT contrast angiography scan of the pulmonary arterial circulation and bilateral venous ultrasound of the proximal leg veins. Patients who were confirmed to have pulmonary embolism or deep vein thrombosis were treated with anticoagulant therapy. Patients in whom the diagnosis of pulmonary embolism was excluded did not receive anticoagulant therapy and were followed for a 3-month period for the development of venous thromboembolic complications. Eight hundred fifty-eight (858) patients were enrolled in this study. Three-hundred sixty-nine (369) patients had low pretest probability and negative D-dimer results and no further diagnostic tests were performed. None of these patients subsequently developed venous thromboembolic complications (0%, 95% confidence interval [CI] 0% to 1.0%). The remaining 489 were referred for spiral CT contrast angiography scan and ultrasound. Sixty-seven patients were confirmed to have pulmonary embolism and an additional 15 patients with negative CT scans had proximal deep vein thrombosis (DVT) on ultrasound for a total prevalence of venous thromboembolism of 82/489 (16.8%). Two of 409 patients who had pulmonary embolism excluded in the initial evaluation phase developed proximal venous thromboembolism (0.5%; 95% CI 0% to 1.8%) in the 3-month follow-up period. These findings suggest that the combination of a negative spiral CT contrast angiography scan and normal venous ultrasound imaging safely excludes the diagnosis of pulmonary embolism in the Emergency Department setting.     

Contribution of indirect computed tomography venography to computed tomography angiography of the chest for the diagnosis of thromboembolic disease in two United States emergency departments

Summary.  Recent reports suggest that physicians in non-ambulatory settings can use indirect CT venography (CTV) of the lower extremities immediately following spiral CT angiography (CTA) of the chest to identify patients with a negative CTA who have thromboembolic disease identified on CTV. We sought to determine the frequency of isolated deep venous thrombosis (DVT) discovered on CTV in emergency department (ED) patients with complaints suggestive of pulmonary embolism (PE) yet having a negative CTA. This study was conducted in a suburban and urban ED where patients with symptoms suspicious for PE were primarily evaluated with CTA and CTV. A total of 800 patients were studied, including 360 from the suburban ED and 440 from the urban ED. 88 (11%) patients were diagnosed with thromboembolic disease by CTA, or CTV, or both. Seventy-three patients had a CTA of the chest that was positive for PE, 42 (5.2%) of whom had evidence of both PE on CTA and DVT on CTV. Fifteen patients (2%, 95% CI = 1–3%) had a negative CTA and were subsequently found to have isolated DVT on CTV, all of whom received anticoagulation therapy. These data suggest that indirect CT venography of immediately following CT angiography of the chest significantly increased the frequency of diagnosed thromboembolic disease requiring anticoagulation in ED patients with suspected PE.     

Burden of illness in venous thromboembolism in critical care: a multicenter observational study

PURPOSE: The frequency of clinically diagnosed venous thromboembolism (VTE) including deep venous thrombosis (DVT) and pulmonary embolism (PE) in medical-surgical critically ill patients is unclear. The objectives of this study were to estimate the prevalence and incidence of radiologically confirmed DVT and PE in medical-surgical intensive care unit (ICU) patients and to determine the impact of prophylaxis on the frequency of these events. MATERIALS AND METHODS: In a retrospective observational cohort study in 12 adult ICUs, we identified prevalent cases (diagnosed in the 24 hours preceding ICU admission up to 48 hours post-ICU admission) and incident cases (diagnosed 48 hours or more after ICU admission and up to 8 weeks after ICU discharge) of upper or lower limb DVT or PE. Deep venous thrombosis was diagnosed by compression ultrasound or venogram. Each DVT was classified as clinically suspected or not clinically suspected in that the latter was diagnosed by scheduled screening ultrasonography. Pulmonary embolism was diagnosed by ventilation-perfusion lung scan, computed tomography pulmonary angiography, echocardiography, electrocardiography, or autopsy. RESULTS: Among 12,338 patients, 252 (2.0%) patients had radiologically confirmed DVT or PE and another 47 (0.4%) had possible DVT or PE. Prevalent DVTs were diagnosed in 0.4% (95% confidence interval [CI], 0.3%-0.5%) of patients and prevalent PEs were diagnosed in 0.4% (95% CI, 0.3%-0.6%). Incident DVTs were diagnosed in 1.0% (95% CI, 0.8%-1.2%) of patients, and incident PEs were diagnosed in 0.5% (95% CI, 0.4%-0.6%). Of patients with incident VTE, 65.8% of cases occurred despite receipt of thromboprophylaxis for at least 80% of their days in ICU. The median (interquartile range) ICU length of stay was similar for patients with DVT (7 [3-17]) and PE (5 [2-8]). For all patients with VTE, ICU mortality was 16.7% (95% CI, 12.0%-21.3%) and hospital mortality was 28.5% (95% CI, 22.8%-34.1%). CONCLUSIONS: Venous thromboembolism appears to be an apparently infrequent, but likely underdiagnosed problem, occurring among patients receiving prophylaxis. Findings suggest the need for increased suspicion among clinicians, renewed efforts at thromboprophylaxis, and evaluation of superior prevention strategies.     

Contribution of indirect computed tomographic venography to the diagnosis of postpartum venous thromboembolism

Summary.  Background:  The diagnostic value of indirect computed tomographic venography (CTV), following thoracic computed tomographic angiography (CTA), has not been specifically evaluated in postpartum patients with suspected pulmonary embolism. Objectives: To assess the diagnostic value of CTV in postpartum venous thromboembolism. Methods: We reviewed all CTA and CTV procedures performed during the last 7 years in our institution for suspected pulmonary embolism during the postpartum period. We focused on the quality of CTA, the rates of positive CTA and isolated positive CTV findings, and alternative diagnoses provided by CTV. Results: Fifty-five CTA and 33 CTV procedures were performed for suspected pulmonary embolism in 47 patients referred between 24 h and 2 months after Cesarean (34 patients) or vaginal (13 patients) delivery. Of the 33 patients who had both CTA and CTV, seven had positive CTA findings and four had isolated positive CTV findings. Thus, the absolute increase in the venous thromboembolism detection rate following CTV was 12.1% [95% confidence interval (CI) 4.0–29.1]. Subcapsular hematoma of the liver or spleen was found on CTV in another two patients without venous thromboembolism. Consequently, CTV had a direct impact on clinical management in six of 33 patients (18%). Conclusion: Our results suggest that postpartum patients with suspected pulmonary embolism have a significant rate of pelvic vein thrombosis and that the use of CTV leads to a 31% relative increase in the detection rate of venous thromboembolism as compared to CTA alone in these patients.     

双源CT一站式扫描诊断急性肺栓塞与深静脉血栓

目的 评价双源CT(DSCT)一站式扫描对急性肺栓塞(PE)及深静脉血栓(DVT)的诊断价值。方法 采用DSCT对56例临床疑诊急性PE患者先行肺动脉成像(CTPA),间隔120~180 s后再行深静脉成像(CTV)。利用MPR和MIP观察PE和DVT分布情况。56例中,12例于CTPA检查发现PE后接受DSA检查。以血管节段为单位,记录双源CT和DSA对PE和DVT的诊断结果,并与DSA检查结果进行比较。结果 12例PE患者中发现DVT 11例,CTPA对肺段及亚段动脉PE的检出率明显高于DSA(χ²=8.34、92.65,P均<0.01),对肺叶动脉及以上级别血管PE的检出率与DSA差异无统计学意义(P均>0.05)。CTV对DVT的检出率与DSA相比差异无统计学意义(χ²=0.667,P=0.414)。以DSA为金标准,CTV评价DVT的敏感度、特异度、准确率分别为92.16%(47/51)、96.49%(55/57)、94.44%(102/108)。结论 双源CT一站式扫描可同时准确地诊断急性PE及DVT。     

CT venography in suspected pulmonary thromboembolism.

Pulmonary embolism (PE) and deep venous thrombosis (DVT) are a continuum and are difficult to diagnose clinically. Combined CT venography and pulmonary angiography (CTVPA) is a single examination that combines multidetector CT pulmonary angiography (CTPA) and CT venography (CTV) of the abdomen, pelvis, and lower extremities, providing "one-stop shopping" for venous thromboembolism without additional venipuncture or i.v. contrast, and it adds only a few additional minutes to scanning time. CTVPA rapidly and accurately examines the deep veins, reveals the presence, absence, and extent of deep venous thrombosis, serves as a baseline, and helps guide patient management. Multiple investigators have reported a high degree of accuracy when CTV is compared with venous ultrasound. There are some pitfalls in image interpretation, especially with regard to mixing artifacts, and there are continuing controversies as to exactly which parts of the abdomen, pelvis, and legs should be scanned routinely, the ideal timing of CTV acquisition relative to contrast injection, and the slice thickness and gap, if any, that should be used.     

Current and future perspectives in imaging of venous thromboembolism

Summary

Several thrombus imaging techniques for the diagnosis of venous thromboembolism (VTE) are available. The most prevalent forms of VTE are deep vein thrombosis of the lower extremities and pulmonary embolism. However, VTE may also occur at unusual sites such as deep veins of the upper extremity and the splanchnic and cerebral veins. Currently, the imaging techniques most widely used in clinical practice are compression ultrasonography and computed tomography (CT) pulmonary angiography. Moreover, single‐photon emission CT, CT venography, positron emission tomography, and different magnetic resonance imaging (MRI) techniques, including magnetic resonance direct thrombus imaging, have been evaluated in clinical studies. This review provides an overview of the technique, diagnostic accuracy and potential pitfalls of these established and emerging imaging modalities for the different sites of venous thromboembolism.     

Association between asymptomatic deep vein thrombosis detected by venography and symptomatic venous thromboembolism in patients undergoing elective hip or knee surgery

BACKGROUND: Venography is commonly used to compare the efficacy of different thromboprophylaxis strategies for preventing deep vein thrombosis (DVT) in patients undergoing total hip replacement (THR) or total knee replacement (TKR). METHODS: We explored the relation between asymptomatic DVT and symptomatic venous thromboembolism (VTE) in patients undergoing THR or TKR treated with standard doses of enoxaparin (30 mg b.i.d. or 40 mg o.d.) by comparing the incidence of asymptomatic DVT in venographic studies with the incidence of symptomatic VTE in studies where venography was not performed. RESULTS: In 10 venographic studies involving 5796 patients, the incidence of asymptomatic DVT after THR was 13.2% [95% CI, 12.2-14.2%] and after TKR was 38.1% (95% CI, 35.5-40.8%). In two studies involving 3500 patients who did not undergo venography, the 90-day incidence of symptomatic VTE after THR was 2.7% (95% CI, 2.1-3.4%) and after TKR was 1.8% (95% CI, 0.9-2.7%). For every symptomatic VTE in THR studies where venography was not performed there were five asymptomatic DVTs in the venographic studies; for TKR, the ratio was 1:21. The incidence of asymptomatic DVT and the symptomatic VTE/asymptomatic DVT ratio was influenced by the venogram reading committee (Gothenburg vs. Hamilton: total DVT after THR, 19.5% vs. 8.7%, P < 0.0001; for TKR, 42.7% vs. 27.2%, P < 0.0001). CONCLUSIONS: Comparisons across trials show a consistent relation between asymptomatic venographic DVT in patients undergoing elective THR or TKR surgery and symptomatic VTE in patients not undergoing venography. Differences exist in the strength of the relation depending on the type of surgery and the venogram reading committee.     

Prevalence and Significance of Nonthromboembolic Findings on Chest Computed Tomography Angiography Performed to Rule Out Pulmonary Embolism: A Multicenter Study of 1,025 Emergency Department Patients

OBJECTIVES: To evaluate the hypothesis that computed tomography (CT) angiography often yields a result interpreted as an alternative diagnosis to pulmonary embolism (PE) in emergency department (ED) patients. METHODS: This was a multicenter, retrospective, and secondary analysis of consecutive patients in three academic emergency departments. ED patients with symptoms suspicious for PE were included. CT angiography was ordered at the discretion of the treating physician; patients were identified by query of the electronic medical record. Board-certified radiologists gave CT readings, which were reviewed by two independent emergency physicians who categorized the non-PE findings into one of four acuity categories: A = requiring specific and immediate intervention, B = requiring specific action on follow-up, C = requiring no action, and D = indeterminate findings. RESULTS: The prevalence of PE among the 1,025 patients studied was 10% (95% CI = 8% to 12%). In the 921 patients without PE, the mean prevalences (ranges between sites) of concordant categorized non-PE findings were: A = 7% (range 3%-11%), B = 10% (7%-13%), C = 17% (10%-20%), D = 4% (0%-8%), and no ancillary finding = 41% (29% to 45%). The most common category A findings included infiltrate or consolidation suggesting pneumonia (81%), aortic aneurysm or dissection (7%), and mass suggesting undiagnosed malignancy (7%). The overall unweighted agreement was 80% (kappa = 0.72) and weighted agreement was 93% (kappa(w) = 0.84). CONCLUSIONS: In ED patients with suspected PE, the CT angiogram frequently provides evidence suggesting an important alternative diagnosis to PE. Pulmonary infiltrate suggesting pneumonia was the most common non-PE finding.     

Treatment of upper‐extremity deep vein thrombosis

Summary. Background: Upper extremity deep vein thrombosis (DVT) can result in fatal pulmonary embolism if not treated. Patients with malignancy may be at particularly high risk. Heparin or low‐molecular‐weight heparin followed by warfarin has been used as standard treatment for lower extremity DVT. However, a paucity of studies exist reporting the efficacy and safety of these regimens in patients with upper extremity DVT. We studied the effectiveness and safety of treatment with dalteparin sodium followed by warfarin and also dalteparin sodium monotherapy for 3 months in patients with confirmed upper extremity DVT. Methods: Consecutive patients with confirmed upper extremity DVT received daily dalteparin sodium for 5–7 days followed by warfarin therapy for 3 months (phase I) or dalteparin sodium monotherapy for 3 months (phase II). The primary outcome measure was the incidence of new symptomatic venous thromboembolism during the 3‐month follow‐up period. The outcome measure of safety was the incidence of major and minor bleeding. Results: Of 631 consecutive patients screened, 74 were eligible and 67 enrolled. No patients receiving either phase I (0%; 95% CI, 0–12%) or phase II (0%; 95% CI, 0–9%) therapy had venous thromboembolism on 3‐month follow‐up. One patient (4%; 95% CI, 0–18%) receiving phase I therapy experienced major bleeding. Five patients died during the follow‐up period; none were attributed to pulmonary embolism. Conclusions: Patients with upper extremity DVT may be treated safely with either dalteparin sodium followed by warfarin or dalteparin sodium monotherapy for 3 months with a good prognosis.     

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.     

A randomized study comparing the efficacy and safety of nadroparin 2850 IU (0.3 mL) vs. enoxaparin 4000 IU (40 mg) in the prevention of venous thromboembolism after colorectal surgery for cancer

BACKGROUND: The optimal thromboprophylactic dosage regimen of low-molecular-weight heparins in high-risk general surgery remains debatable. OBJECTIVES: We performed a randomized, double-blind study to compare the efficacy and safety of nadroparin 2850 IU (0.3 mL) and enoxaparin 4000 IU (40 mg) in the prevention of venous thromboembolism (VTE) after colorectal surgery for cancer. Patients and methods: Patients undergoing resection of colorectal adenocarcinoma were randomized to receive once daily either 2850 IU nadroparin or 4000 IU enoxaparin s.c. for 9 +/- 2 days. The primary efficacy outcome was the composite of deep vein thrombosis (DVT) detected by bilateral venography or documented symptomatic DVT or pulmonary embolism up to day 12. The main safety outcome was major bleeding. A blinded independent committee adjudicated all outcomes. RESULTS: Out of 1288 patients analyzed, efficacy was evaluable in 950 (73.8%) patients. The VTE rate was 15.9% (74/464) in nadroparin-treated patients and 12.6% (61/486) in enoxaparin-treated patients, a relative risk of 1.27 (95% confidence interval; CI: 0.93-1.74) that did not met the criterion for non-inferiority of nadroparin. The rate of proximal DVT was comparable in the two groups (3.2% vs. 2.9%, respectively), but that of symptomatic VTE was lower in nadroparin-treated patients (0.2% vs. 1.4%). There was significantly (P = 0.012) less major bleeding in nadroparin- than in enoxaparin-treated patients (7.3% vs. 11.5%, respectively). CONCLUSION: Compared with those receiving enoxaparin 4000 IU, patients treated with nadroparin 2850 IU showed a higher incidence of asymptomatic distal DVT, but a lower incidence of symptomatic VTE. Nadroparin treatment was safer in terms of bleeding risk.     

Deep-vein thrombosis rates after major orthopedic surgery in Asia. An epidemiological study based on postoperative screening with centrally adjudicated bilateral venography

BACKGROUND: The incidence of postsurgical venous thromboembolism is thought to be low in Asian ethnic populations. OBJECTIVE: We studied the incidence of deep-vein thrombosis (DVT) in Asian patients undergoing major orthopedic surgery of the lower limbs. PATIENTS/METHODS: We performed a prospective epidemiological study in 19 centers across Asia (China, Indonesia, South Korea, Malaysia, Philippines, Taiwan, and Thailand) in patients undergoing elective total hip replacement (THR), total knee replacement (TKR) or hip fracture surgery (HFS) without pharmacological thromboprophylaxis. The primary endpoint was the rate of DVT of the lower limbs documented objectively with bilateral ascending venography performed 6-10 days after surgery using a standardized technique and evaluated by a central adjudication committee unaware of local interpretation. RESULTS: Overall, of 837 Asian patients screened for this survey, 407 (48.6%, aged 20-99 years) undergoing THR (n = 175), TKR (n = 136) or HFS (n = 96) were recruited in 19 centers. DVT was diagnosed in 121 of 295 evaluable patients [41.0%, (95% confidence interval (CI): 35.4-46.7)]. Proximal DVT was found in 30 patients [10.2% (7.0-14.2)]. Total DVT and proximal DVT rates were highest in TKR patients (58.1% and 17.1%, respectively), followed by HFS patients (42.0% and 7.2%, respectively), then THR patients (25.6% and 5.8%, respectively). DVT was more frequent in female patients aged at least 65 years. Pulmonary embolism was clinically suspected in 10 of 407 patients (2.5%) and objectively confirmed in two (0.5%). CONCLUSIONS: The rate of venographic thrombosis in the absence of thromboprophylaxis after major joint surgery in Asian patients is similar to that previously reported in patients in Western countries.     

The Probability of Pulmonary Embolism Is a Function of the Diagnoses Considered Most Likely Before Testing

Objectives: To determine the frequency of pulmonary embolism (PE) diagnosis when different alternative diagnoses were considered most likely before testing, because the relationship between specific alternative diagnoses and the diagnosis of PE has not been explored.
Methods: This study was a preplanned secondary analysis of a prospective study of the diagnosis of pulmonary embolism conducted in the emergency department (ED) of an urban university hospital. Physicians were queried as to their most likely pretest diagnosis when they ordered any of the following tests to evaluate possible PE: D-dimer, contrast-enhanced computed tomography of the chest, ventilation–perfusion lung scan, or pulmonary angiogram. To compare the frequency of PE diagnosis across alternative diagnoses, risk ratios, 95% confidence intervals (CI), and p-values using Fisher's exact test were calculated.
Results: Six hundred seven patients were enrolled, and 61 had PE. Physicians thought PE was the most likely pretest diagnosis in 162 (26.7%) patients, and 20.4% (95% CI = 14.4% to 27.4%) of these patients had PE. For four alternative diagnoses, PE was diagnosed less frequently than when PE was considered most likely: musculoskeletal pain (2.2%, 95% CI = 0.4% to 6.2%), anxiety (1.7%, 95% CI = 0.0 to 9.2%), asthma or chronic obstructive pulmonary disease (0, 95% CI = 0.0 to 10.9%), and viral syndrome (0, 95% CI = 0.0 to 14.3%).
Conclusions: The frequency of PE is related to the most likely pretest alternative diagnosis. PE is diagnosed infrequently when anxiety, asthma or chronic obstructive pulmonary disease, musculoskeletal pain, or viral syndrome is the most likely alternative diagnosis.     

Extended prophylaxis with bemiparin for the prevention of venous thromboembolism after abdominal or pelvic surgery for cancer: the CANBESURE randomized study

Summary. Background: There is not enough clinical evidence to make a strong recommendation on the optimal duration of thromboprophylaxis using low‐molecular weight heparins (LMWH) in patients undergoing major cancer surgery. Patients and methods: CANBESURE is a randomized, double‐blind study which enrolled patients admitted for abdominal or pelvic surgery for cancer. They received 3500 IU of bemiparin subcutaneously once daily for 8 days and were then randomized to receive either bemiparin or placebo for 20 additional days. Bilateral venography was performed after 20 days and evaluated blinded. The primary efficacy outcome was the composite of deep vein thrombosis (DVT), non‐fatal pulmonary embolism (PE) and all‐cause mortality at the end of double‐blind period. Major venous thromboembolism (proximal deep‐vein thrombosis, non‐fatal pulmonary embolism and venous thromboembolism‐related deaths) was also evaluated. The primary safety outcome was major bleeding. Results: Six hundred and twenty‐five and 488 patients were included in the safety and main efficacy analyzes, respectively. The primary efficacy outcome occurred in 25 out of 248 patients (10.1%) in the bemiparin group and 32 out of 240 (13.3%) in the placebo group (relative risk reduction 24.4%; 95% CI: ?23.7–53.8%; P = 0.26). At the end of double‐blind period, major venous thromboembolism occurred in 2 (0.8%) and 11 (4.6%) patients, respectively (relative risk reduction 82.4%; 95% CI: 21.5–96.1%; P = 0.010). No significant difference was found in major bleedings. Conclusions: Four weeks compared with 1 week of prophylaxis with bemiparin after abdominal or pelvic cancer surgery did not significantly reduce the primary efficacy outcome, but decreased major venous thromboembolism (VTE) without increasing hemorrhagic complications.     

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.     

Systematic Bias Introduced by the Informed Consent Process in a Diagnostic Research Study

Objectives:  To determine population characteristics, outcomes, and reasons for unsuccessful enrollment among potential study subjects approached for written, informed consent in a minimal-risk emergency department (ED) study. The authors hypothesized that the prevalence of venous thromboembolism (VTE) would be lower among study participants and that medical acuity and refusal to provide a blood sample would be the most common reasons for nonparticipation.
Methods:  The authors requested prospective, written, informed consent for a blood sample and follow-up from consecutive ED patients undergoing evaluation for pulmonary embolism (PE) and recorded spontaneously stated reasons for refusal. VTE was diagnosed or excluded using a combination of D-dimer testing and selective computed tomography (CT) angiography of the chest with venography of the lower extremities. The primary outcome was defined by the number of CT scans positive for VTE among ED patients evaluated for PE.
Results:  Over 16 weeks, 260 of 287 (91%, 95% confidence interval [CI] = 87 to 94%) eligible patients were approached and consent was obtained from 183 patients (64%, 95% CI = 58% to 69%). The prevalence of VTE was 6% among participants and 13% among nonparticipants (95% CI [of the difference] = 1% to 15%). The proportions of African Americans, uninsured, and Medicaid patients were significantly higher among nonparticipants. No significant differences were found in the proportions of nonparticipants who disliked or distrusted research or desired financial reimbursement, compared to those not enrolled due to medical acuity or refused a blood sample.
Conclusions:  These data implicate the written, informed consent process as a significant source of bias on estimated disease prevalence.     

A phase II study of the oral factor Xa inhibitor LY517717 for the prevention of venous thromboembolism after hip or knee replacement

BACKGROUND: LY517717 is an oral direct inhibitor of activated factor X that is currently under clinical development. OBJECTIVES: The aims of this proof-of-concept study in patients undergoing total knee replacement (TKR) or total hip replacement (THR) were to determine whether LY517717 can safely reduce the risk of venous thromboembolism (VTE) and to identify at least one dose of LY517717 that is non-inferior to enoxaparin. METHODS: In a double-blind, parallel-arm, dose-ranging study, patients undergoing TKR or THR were randomly allocated to receive once-daily oral LY517717 (25, 50, 75, 100, 125 or 150 mg), started 6-8 h after wound closure, or s.c. enoxaparin, 40 mg, started in the evening before surgery. The primary efficacy endpoint was the composite of deep venous thrombosis (DVT), detected by mandatory bilateral venography performed at the end of the study treatment (between days 5 and 9), and objectively confirmed symptomatic DVT and/or pulmonary embolism (PE), occurring during the treatment period. The combination of major and minor bleeding was the primary safety endpoint. RESULTS: Five hundred and seven patients received at least one dose of LY517717 or enoxaparin (safety population). Three hundred and ninety-one patients had evaluable bilateral venography or experienced a clinical DVT and/or PE (primary efficacy population). LY517717 treatment resulted in a dose-dependent decrease in the incidence of thromboembolic events (P = 0.0001). The incidences of VTE with 100, 125, and 150 mg of LY517717 were 19%, 19% and 16%, respectively, compared to 21% with enoxaparin. The efficacies of 100-mg, 125-mg and 150-mg doses of LY517717 were non-inferior to that of enoxaparin according to prespecified criteria. Bleeding events were uncommon in both LY517717 and enoxaparin patients. CONCLUSIONS: Doses of 100, 125 and 150 mg of LY517717 are non-inferior to enoxaparin for the prevention of VTE after TKR or THR, and are associated with similar low rates of bleeding.     

The technique of occlusive-cuff impedance plethysmography. How to use this sensitive, noninvasive tool to detect proximal DVT

Occlusive-cuff impedance plethysmography (IPG) is a rapid, reliable, and noninvasive method of diagnosing proximal deep venous thrombosis (DVT) in the lower extremities. The test is relatively easy to perform and carries an overall accuracy of greater than 90% when compared with venography. IPG is useful in detecting acute, symptomatic DVT and in determining the presence of recurrent DVT. In certain patients with nondiagnostic lung scans in whom pulmonary embolism is suspected, IPG may be helpful in determining appropriate therapy without use of pulmonary angiography.     

血栓弹力图在下肢深静脉血栓与肺栓塞的应用价值

[目的]探讨血栓弹力图对下肢深静脉血栓形成(DVT)患者与DVT合并肺栓塞(PE)患者的应用价值.[方法]选择2014年3~9月本院收治的新发DVT及DVT合并PE患者12例,其中新发DVT患者8例,DVT合并PE患者4例,选择同期无DVT或PE病史的12例健康体检者为对照组,均行下肢静脉彩超、肺动脉CT血管成像(CTA)、血栓弹力图等检查.比较DVT患者及DVT合并PE患者在血栓弹力图相关指标如凝血反应时间(R值)、凝固时间(K值)、最大血凝块强度(MA)、凝固角(Angel)、凝血综合指数(CL)的异同点.[结果]DVT组、DVT合并PE组与对照组在年龄、性别、R、MA、K、Angel、CL方面比较,组间比较差异无统计学意义(P>0.05).[结论]下肢深静脉血栓形成与下肢深静脉血栓形成合并肺栓塞在血栓弹力图指标上无明显差异,血栓弹力图在VTE中的应用价值尚需进一步研究.