Current treatment strategies for primary upper extremity deep venous thrombosis; a retrospective observational multicenter case series.

Introduction: Current treatment strategies for primary upper extremity deep venous thrombosis (pUEDVT) range from conservative treatment with anticoagulation therapy to invasive treatment with thoracic outlet decompression surgery (TOD), frequently combined with catheter directed thrombolysis, percutaneous transluminal angioplasty, or stenting. Due to a lack of large prospective series with uniform data collection or a randomized trial, the optimal treatment strategy is still under debate. We conducted a multicenter observational study to assess the efficacy and safety of both the conservative and invasive treatment strategies for patients with pUEDVT. Methods: We retrospectively collected data from patients treated in five vascular referral and teaching hospitals in the Netherlands between 2008 and 2019. Patients were divided into a conservative (Group 1), an invasive treatment group (Group 2) and a cross-over group (Group 3) of patients who received surgical treatment after initial conservative therapy. Follow-up consisted of outpatient clinic visits and an electronic survey. Primary outcome was symptom free survival defined as absence of any symptom of the affected arm reported at last follow-up regardless of severity, or extent of functional disability. Secondary outcomes were incidence of bleeding complications, recurrent venous thromboembolism, surgical complications, and reinterventions. Results: A total of 115 patients were included (group 1 (N = 45), group 2 (N = 53) or group 3 (N = 27). The symptom free survival was 35.6%, 54.7% and 48.1% after a median follow-up of 36, 26 and 22 months in groups 1, 2 and 3 respectively. Incidence of bleeding complications was 8.6%, 3.8% and 18.5% and recurrent thrombosis occurred in 15.6%, 13.2% and 14.8% in groups 1-3 respectively. Conclusion: In this multicenter retrospective observational cohort analysis the conservative and direct invasive treatments for pUEDVT were deemed safe with low percentages of bleeding complications. Symptom free survival was highest in the direct surgical treatment group but still modest in all subgroups. Perioperative complications were infrequent with no related long term morbidity. Of relevance, pUEDVT patients with confirmed VTOS and recurrent symptoms after conservative treatment may still benefit from TOD surgery. However, symptom free survival of this delayed TOD seems lower than direct surgical treatment and bleeding complications seem to occur more frequently.

Effect of an interactive, educational app about venous thromboembolism and anticoagulation on patient satisfaction: A randomized controlled trial.

BACKGROUND: Adequate patient education is essential for patients to engage in shared decision-making when deciding to stop or continue anticoagulation after 3 months for venous thromboembolism (VTE). Our objectives were to evaluate the effect of an interactive, educational app on patients' level of satisfaction with information, perceived level of knowledge, decisional conflict and extent of shared decision-making when deciding on treatment duration of VTE. MATERIALS AND METHODS: This randomized controlled trial in 1 academic and 3 general Dutch hospitals included adult patients diagnosed with VTE without malignancy or prolonged anticoagulation for other indications. Patients were randomized in 1:1 ratio to receive the app (intervention group) in addition to hospital-specific standard of care. The app, created for this study, contains information on VTE and anticoagulation on an interactive timeline. In the week preceding the consultation when treatment duration is decided, patients were provided with daily videos using push notifications. Outcomes were assessed through self-reported questionnaires at baseline, 1-2 days before and 1 day after consultation. Data were analyzed using t-tests and linear mixed models for repeated measurements. RESULTS: Data of 56 patients were analyzed (mean age 57 ± 13; 27% female). On a numeric rating scale from 0 to 10, patients who received the app were 0.9 points (95%CI 0.0-1.7; p 0.04) more satisfied with the provided information. Patients who received the app experienced significantly less decisional conflict. No differences in other outcomes were observed. CONCLUSIONS: An educational app about VTE and anticoagulation increases patients' satisfaction and reduces decisional conflict when deciding on treatment duration of VTE. This study was registered in the Netherlands Trial Register (NL7037).

Dalteparin and anti-Xa: a complex interplay of therapeutic drug monitoring.

BACKGROUND: Monitoring low-molecular-weight heparins is generally not required. However, guidelines advise to monitor anti-Xa levels in patients with renal insufficiency or a BMI above 50, and in pregnancy. Measuring anti-Xa levels is a complex challenge since sampling should be performed three to five hours after subcutaneous injection and after steady state concentrations have been reached. Strict compliance is pivotal for justified dose adjustments. OBJECTIVES: We questioned compliance to our protocol and performed this study to explore that. METHODS: This retrospective cohort study included patients ≥ 18 years receiving therapeutic dalteparin in a Dutch academic medical centre. Patients with a first anti-Xa level measured between February 23rd and December 30th, 2017 were selected. According to our local guideline, monitoring anti-Xa activity is indicated in patients on therapeutic doses of dalteparin who are pregnant, morbidly obese (BMI > 50), or have renal insufficiency (clearance < 60 ml/min). Accurate sampling was defined as measuring levels after at least three injections (after which a patient may reach steady state) and then four hours after the injection with dalteparin. The frequency of compliance to our protocol was assessed. RESULTS: We included 158 patients with 396 anti-Xa levels, of which 41% (65/158) of all first anti-Xa levels were drawn without appropriate indication. Almost half, 48% (211/396), were sampled incorrectly and 25% of these (53/211) were followed by a dose adjustment. In total, 74% (293/396) of the samples were not indicated or were taken at the wrong time. CONCLUSIONS: Monitoring anti-Xa levels is a complex clinical challenge. This study showed that non-compliance with recommendations for anti-Xa monitoring was high, often resulting in unjustified dose adjustments.

Rationale for catheter-based therapies in acute pulmonary embolism.

Pulmonary embolism (PE) is a common disease resulting in significant morbidity and mortality. High-risk features of PE are hypotension or shock, and early reperfusion is warranted to unload the strained right ventricle and improve clinical outcomes. Currently, systemic thrombolysis (ST) is the standard of care but is associated with bleeding complications. Catheter-based therapies (CDT) have emerged as a promising alternative having demonstrated to be equally effective while having a lower risk of bleeding. Several CDT are currently available, some combining mechanical properties with low-dose thrombolytics. Recent guidelines suggest that CDT may be considered in patients with high-risk PE who have high bleeding risk, after failed ST, or in patients with rapid haemodynamic deterioration as bail-out before ST can be effective, depending on local availability and expertise. In haemodynamically stable patients with right ventricular (RV) dysfunction (intermediate-risk PE), CDT may be considered if clinical deterioration occurs after starting anticoagulation and relative contraindications for ST due to bleeding risk exist. Decision on treatment modality should follow a risk-benefit analysis on a case by case base, weighing the risk of PE-related complications; i.e. haemodynamic deterioration vs. bleeding. As timely initiation of treatment is warranted to prevent early mortality, bleeding risk factors should be assessed at an early stage in all patients with acute PE and signs of RV dysfunction. To ensure optimal management of complex cases of PE and assess a potential CDT strategy, a multidisciplinary approach is recommended. A dedicated Pulmonary Embolism Response Team may optimize this process.

No added value of the age-adjusted D-dimer cut-off to the YEARS algorithm in patients with suspected pulmonary embolism.

Essentials Imaging is warranted in the majority of patients to confirm or rule out pulmonary embolism (PE). The age-adjusted D-dimer (ADJUST) reduced the number of required imaging tests in patients ≥ 50 years. The YEARS algorithm was designed to improve the efficiency in patients with suspected PE. There was no added value of implementing ADJUST in the YEARS algorithm in our cohort. SUMMARY: Background The YEARS algorithm was designed to simplify the diagnostic work-up of pulmonary embolism (PE) and to reduce the number of necessary computed tomography pulmonary angiography (CTPA) scans. An alternative strategy to reduce the number of CTPAs is the age-adjusted D-dimer cut-off (ADJUST) in patients aged 50 years or older. We aimed to investigate whether a combination of both diagnostic strategies might save additional CTPAs. Methods The YEARS algorithm consists of three items (clinical signs of deep venous thrombosis, hemoptysis, 'PE most likely diagnosis') with simultaneous D-dimer testing using a pre-test dependent threshold. We performed a post hoc analysis in 3465 patients managed according to YEARS to compare the number of patients managed without CTPA scans and associated diagnostic failures in hypothetical scenarios with different YEARS-ADJUST combinations. Results Following the YEARS algorithm, 1651 patients (48%) were managed without CTPA; PE was diagnosed in 456 (13%) patients at baseline and 18 patients with initial normal testing suffered venous thromboembolism (VTE) during 3-month follow-up (failure rate 0.61%; 95% confidence interval [CI], 0.36-0.96). If ADJUST had been fully integrated in YEARS, 1627 patients (47%) would have been managed without CTPA (absolute decrease of 0.69%; 95% CI -1.7 to 3.0), at cost of four additional missed PE diagnoses at baseline, for a projected 3-month VTE failure rate of 0.75% (95% CI, 0.49-1.13). None of the other studied scenarios showed relevant improvements in efficiency as well, but all led to more missed diagnoses. Conclusion In our cohort, there was no added value of implementing ADJUST in the YEARS algorithm.

Plasma levels of microparticle-associated tissue factor activity in patients with clinically suspected pulmonary embolism.

INTRODUCTION: Microparticles (MPs) carrying active tissue factor (TF) have been detected in the plasma of cancer patients in particular in those presenting with acute deep vein thrombosis (DVT) or pulmonary embolism (PE). Experimental studies in mice have revealed that circulating MPs carrying TF contribute to thrombus formation. AIM: To study whether unselected patients with an acute confirmed PE have elevated TF activity in the MP fraction (MP-TF activity). MATERIALS AND METHODS: Plasma MP-TF activity was measured in 159 non-selected patients with clinically suspected PE and in 48 healthy controls as previously described. Blood was collected at time of inclusion. The diagnosis of acute PE was confirmed in 54 patients and excluded in 105 patients. RESULTS: Median MP-TF activity in 159 patients with clinically suspected PE was 72 fM Xa/min [range 32-6657] fM Xa/min and higher than in healthy controls (66 [range 28-183] fM Xa/min; P<0.05). There was no significant difference (P=0.169) in MP-TF activity between patients with confirmed PE (median 84.5 fM Xa/min [range 36-2149]) and patients without PE (72 fM Xa/min [range 32-6657]) fM Xa/min). In the 159 patients with clinically suspected PE we observed in an exploratory analysis higher MP-TF activity levels in patients with active cancer (median 137 fM Xa/min [range 36-6657]) and cardiovascular disease (median 131.5 fM Xa/min [range 45-2149]) than in patients without these disorders (P=0.0004 and P=0.014, respectively). CONCLUSION: In patients presenting with clinically suspected PE plasma MP-TF activity was not associated with confirmed PE.

Comparison of the clinical usefulness of two quantitative D-Dimer tests in patients with a low clinical probability of pulmonary embolism.

BACKGROUND: Quantitative D-Dimer tests are established methods in the non-invasive diagnostic management to rule out venous thromboembolism (VTE). The diagnostic performance and the clinical efficiency different D-Dimer assays in the exclusion of pulmonary embolism (PE) have not yet been compared in a clinical outcome study. OBJECTIVE: Evaluation of the efficiency and safety of excluding the diagnosis of PE with two different quantitative D-Dimer assays in consecutive patients with clinically suspected PE. PATIENTS AND METHODS: We studied the VTE-failure rate of 2206 consecutive patients with an unlikely clinical probability in whom VIDAS or Tinaquant D-Dimer tests were performed. RESULTS: The prevalence of PE in 1238 patients whose D-Dimer level was analyzed with Tinaquant assay was 11%. The VIDAS assay group consisted of 968 patients with a PE prevalence of 13%. The VIDAS assay had a sensitivity of 99.2% (95%CI; 96- >99.9%), the Tinaquant assay of 97.3% (95%CI; 93 -99%). The negative predictive value (NPV) in the Tinaquant assay group was 99.4% (95%CI 98-99.8%) in comparison to 99.7% (95%CI 99->99.9%) in the VIDAS assay group. During 3 month of follow-up, there were no fatal cases of PE among patients with normal D-Dimer and unlikely clinical probability in both D-Dimer assay groups. In addition, the test efficiency of Tinaquant assay was significantly higher in comparison to VIDAS assay (52% vs 42%, p<0.001). CONCLUSION: Both Tinaquant and VIDAS D-Dimer tests perform equally well in combination with an unlikely clinical probability in excluding PE. The Tinaquant test was shown to be more efficient.

High D-dimer levels increase the likelihood of pulmonary embolism.

Objective. To determine the utility of high quantitative D-dimer levels in the diagnosis of pulmonary embolism. Methods. D-dimer testing was performed in consecutive patients with suspected pulmonary embolism. We included patients with suspected pulmonary embolism with a high risk for venous thromboembolism, i.e. hospitalized patients, patients older than 80 years, with malignancy or previous surgery. Presence of pulmonary embolism was based on a diagnostic management strategy using a clinical decision rule (CDR), D-dimer testing and computed tomography. Results. A total of 1515 patients were included with an overall pulmonary embolism prevalence of 21%. The pulmonary embolism prevalence was strongly associated with the height of the D-dimer level, and increased fourfold with D-dimer levels greater than 4000 ng mL(-1) compared to levels between 500 and 1000 ng mL(-1). Patients with D-dimer levels higher than 2000 ng mL(-1) and an unlikely CDR had a pulmonary embolism prevalence of 36%. This prevalence is comparable to the pulmonary embolism likely CDR group. When D-dimer levels were above 4000 ng mL(-1), the observed pulmonary embolism prevalence was very high, independent of CDR score. Conclusion. Strongly elevated D-dimer levels substantially increase the likelihood of pulmonary embolism. Whether this should translate into more intensive diagnostic and therapeutic measures in patients with high D-dimer levels irrespective of CDR remains to be studied.

High D-dimer level is associated with increased 15-d and 3 months mortality through a more central localization of pulmonary emboli and serious comorbidity.

High D-dimer levels are predictors of death in patients with pulmonary embolism (PE), as are more proximally located, larger emboli. The direct link between these three has not yet been described. A cohort of 674 consecutive patients with confirmed PE was studied. Patients were followed up for 3 months. D-dimer levels were measured only in patients with an unlikely clinical probability (n = 262). The odds ratio (OR) for death of all variables was calculated. Multivariate analysis was performed to identify independent risk factors for mortality. The best predictive D-dimer cut-off point for mortality was a concentration >3000 ng/ml FEU (OR 7.29). High D-dimer levels were correlated with active malignancy and age over 65 years, both being indicators of 3-month mortality. High D-dimer levels were also correlated with centrally located pulmonary emboli and 15-d mortality. The combination of high D-dimer levels and central emboli increased early mortality risk by 2.2. High D-dimer levels in patients with an unlikely clinical probability were associated with fatal outcome after PE. Centrally located pulmonary emboli were associated with higher D-dimer levels and worse 15-d mortality. Active malignancy, being an inpatient at time of diagnosis and age over 65 years were associated with higher D-dimer levels and worse 3-month survival.

Comparison of the revised Geneva score with the Wells rule for assessing clinical probability of pulmonary embolism.

BACKGROUND: The revised Geneva score, a standardized clinical decision rule in the diagnosis of pulmonary embolism (PE), was recently developed. The Wells clinical decision is widely used but lacks full standardization, as it includes subjective clinician's judgement. We have compared the performance of the revised Geneva score with the Wells rule, and their usefulness for ruling out PE in combination with D-dimer measurement. METHODS: In 300 consecutive patients, the clinical probability of PE was assessed prospectively by the Wells rule and retrospectively using the revised Geneva score. Patients comprised a random sample from a single center, participating in a large prospective multicenter diagnostic study. The predictive accuracy of both scores was compared by area under the curve (AUC) of receiver operating characteristic (ROC) curves. RESULTS: The overall prevalence of PE was 16%. The prevalence of PE in the low-probability, intermediate-probability and high-probability categories as classified by the revised Geneva score was similar to that of the original derivation set. The performance of the revised Geneva score as measured by the AUC in a ROC analysis did not differ statistically from the Wells rule. After 3 months of follow-up, no patient classified into the low or intermediate clinical probability category by the revised Geneva score and a normal D-dimer result was subsequently diagnosed with acute venous thromboembolism. CONCLUSIONS: This study suggests that the performance of the revised Geneva score is equivalent to that of the Wells rule. In addition, it seems safe to exclude PE in patients by the combination of a low or intermediate clinical probability by the revised Geneva score and a normal D-dimer level. Prospective clinical outcome studies are needed to confirm this latter finding.

A simple diagnostic strategy in hospitalized patients with clinically suspected pulmonary embolism.

OBJECTIVES: Diagnostic strategies in patients with suspected pulmonary embolism have been extensively studied in outpatients; their value in hospitalized patients has not been well established. Our aim was to determine the safety and clinical utility of a simple diagnostic strategy in hospitalized patients with suspected pulmonary embolism. DESIGN: Prospective management study. SETTING: Twelve teaching hospitals (five academic, seven general hospitals). SUBJECT: A total of 605 hospitalized patients with clinically suspected pulmonary embolism. All patients completed the study. INTERVENTIONS: First the clinical decision rule (CDR)-score was calculated. An unlikely CDR-score in combination with a normal D-dimer excluded pulmonary embolism. All other patients underwent helical computed tomography (CT). CT either diagnosed or excluded pulmonary embolism, in which case anticoagulants were started or withheld. All patients were instructed to report symptoms of venous thrombosis. Objective tests were performed to confirm venous thromboembolism. The primary outcome was the incidence of symptomatic venous thrombosis during 3-month follow-up. RESULTS: The combination of an unlikely CDR-score and a normal D-dimer excluded pulmonary embolism in 60 patients (10% of all patients); no venous thromboembolic event occurred during follow-up (0%; 95% CI 0-6.7%). CT excluded pulmonary embolism in 380 patients; during follow-up venous thromboembolism occurred in five patients (1.4%; 95% CI 0.4-3.1%). CONCLUSIONS: An unlikely CDR-score in combination with a normal D-dimer appears to exclude pulmonary embolism safely in hospitalized patients. Before clinical implementation it is important this safety is confirmed by others. CT testing was obviated in only 10% of patients. CT can safely exclude pulmonary embolism in hospitalized patients.

Accuracy of clinical decision rule, D-dimer and spiral computed tomography in patients with malignancy, previous venous thromboembolism, COPD or heart failure and in older patients with suspected pulmonary embolism.

BACKGROUND: The diagnostic work-up of patients with suspected pulmonary embolism (PE) has been optimized and simplified by the use of clinical decision rules (CDR), D-dimer (DD) testing and spiral computed tomography (s-CT). Whether this strategy is equally safe and efficient in specific subgroups of patients is evaluated in this study. METHODS: A diagnostic strategy including a CDR, DD test and s-CT was evaluated in patients with malignancy, previous venous thromboembolism (VTE), chronic obstructive pulmonary disease or heart failure and in older patients. PE was ruled out by either an unlikely CDR and a normal DD or a s-CT negative for PE. The safety of these tests was assessed by the 3-month incidence rate of symptomatic VTE in those without PE at baseline. The efficiency was evaluated by calculating the numbers needed to test for the different subgroups. RESULTS: The venous thromboembolic incidence rate after the combination of an unlikely CDR and a normal DD varied from 0% (95% CI: 0-7.9%) in the 482 patients older than 75 years of age to 2% (95% CI: 0.05-10.9%) in the 474 patients with a malignancy. For s-CT these incidences varied from 0.3% to 1.8%. The number needed to test in order to rule out one patient from PE with the studied strategy was highest in cancer patients and in the elderly patients (approximately 10). CONCLUSION: It appears to be safe to rule out PE by either the combination of an unlikely CDR and a normal DD or by a negative s-CT in various subgroups of patients with suspected PE. However, the clinical usefulness of the CDR in combination with the DD as the initial step in the diagnostic process varied among these patient groups.

Diagnosis of deep vein thrombosis and pulmonary embolism in pregnancy: a systematic review.

INTRODUCTION: Diagnosing deep vein thrombosis (DVT) and pulmonary embolism (PE) in pregnancy is challenging. Many of the common diagnostic tests, including compression ultrasonography (CUS), ventilation-perfusion scintigraphy (VQ scan) and helical computed tomography (hCT) that have been extensively investigated in non-pregnant patients, have not been appropriately validated in pregnancy. Extrapolating results of diagnostic studies of DVT and PE in non-pregnant patients to those who are pregnant may not be correct because during pregnancy, physiologic and anatomic changes may affect diagnostic test results, presentation and natural history of VTE. METHODS: We performed a systematic analysis of published studies addressing accurate diagnostic testing for DVT and PE in pregnancy to determine the accuracy of these tests in pregnancy. RESULTS: Our initial search yielded 530 articles of which four remained for inclusion, three studies investigating diagnostic testing in patients with a clinical suspicion of DVT or PE and one study in patients with a clinical suspicion of PE. CONCLUSIONS: From our systematic analysis of published studies investigating diagnostic testing for a clinical suspicion of DVT in pregnancy we conclude that; (i) two studies support withholding anticoagulant therapy in pregnant women with a clinical suspicion of DVT and normal results on serial IPG (impedance plethysmography), however, IPG is no longer used; (ii) one study demonstrated that a normal CUS at presentation combined with a normal D-dimer test or an abnormal D-dimer test combined with normal serial CUS appears promising for safely excluding DVT in pregnant patients, but too few patients were included in this pilot-study to draw firm conclusions; and (iii) one study investigated pregnant patients with a clinical suspicion of PE and this study concluded that in patients with normal or non-diagnostic VQ scans, withholding anticoagulant therapy might be safe, but this needs confirmation in larger studies. Recommendations on diagnostic testing of pregnant patients with a clinically suspected DVT or PE are provided.

Diagnostic methods in pulmonary embolism.

Diagnosing pulmonary embolism (PE) is challenging since clinical signs and symptoms are non-specific. The diagnostic tests available for demonstrating PE all have their drawbacks and are often costly and consume considerable amounts of resources. Simple tools that have become available in the last several years include clinical prediction rules and D-dimer testing. Assessment of the clinical probability, combined with a D-dimer test, can limit the need for additional diagnostic tests by 30%. For outpatients with a normal, sensitive ELISA D-dimer test and a low-to-moderate clinical probability, PE can safely be ruled out. Pulmonary angiography, though still the gold standard, is rarely used nowadays because of its invasiveness, its high costs and limited availability, and the declining experience of radiologists with the technique. Two imaging techniques--lung scintigraphy and helical CT--are the diagnostic methods of choice. A normal perfusion lung scan can safely exclude PE. However, 55-65% of patients have indeterminate lung scan results, making additional imaging tests necessary. Helical CT is increasingly being used as the first-line test because it can directly visualize a thromboembolus, it can suggest an alternative diagnosis, and there is excellent inter-observer agreement. A normal helical CT, followed by compression ultrasonography of the leg veins, can safely rule out PE. Finally, the safety of withholding anticoagulant treatment from patients with a normal multi-row detector helical CT as the sole test has not yet been demonstrated.

Pentasaccharides in the prophylaxis and treatment of venous thromboembolism: a systematic review.

PURPOSE OF REVIEW: The aim of this review is to perform a critical analysis of all completed studies evaluating pentasaccharides-synthetically derived, selective inhibitors of activated factor X-in prophylaxis in major orthopedic surgery and the treatment of venous thromboembolism. RECENT FINDINGS: Venous thromboembolism is a disorder with considerable morbidity when left untreated. New antithrombotic agents have been developed that selectively inhibit components of the coagulation system, thereby avoiding the difficulties associated with current anticoagulants. The pentasaccharides fondaparinux and idraparinux are the first of a new class of synthetic selective inhibitors of activated factor X. Fondaparinux has been extensively investigated in two areas: orthopedic surgery and venous thromboembolism. It is clear from four thromboprophylaxis studies in major orthopedic surgery that fondaparinux is 50% more effective in reducing venous thromboembolism than enoxaparin. This superior efficacy led to an overall increase in major bleeding, which was however primarily due to more fondaparinux-treated patients with bleeding indexes of 2 or greater. The incidence of fatal bleeding, critical organ bleeding, or bleeding leading to reoperation did not differ significantly between the two groups. In the initial treatment of patients with proximal vein thrombosis and pulmonary embolism, fondaparinux was equally effective as low molecular weight heparins and unfractionated heparin, respectively, without a different incidence in major bleeding in fondaparinux and comparator heparin groups. SUMMARY: Fondaparinux, one of the first of a new class of synthetic selective factor Xa inhibitors, is overall 50% more effective in reducing venous thromboembolism than enoxaparin in major orthopedic surgery, with an overall 1% increased rate of major bleeding, when compared with enoxaparin. The incidence of fatal bleeding, critical organ bleeding, or bleeding leading to reoperation did not differ significantly between the two treatment groups. Fondaparinux is equally effective as low molecular weight heparins and unfractionated heparin in the initial treatment of patients with proximal vein thrombosis and pulmonary embolism, respectively. Finally, as with any new drug, fondaparinux should be used cautiously and only in patients who reflect the population of the clinical trials in which the drug was evaluated.

The role of helical CT in the diagnosis of pulmonary embolism.

Diagnosing pulmonary embolism is problematic since clinical signs and symptoms of PE are aspecific. Diagnostic algorithms have been developed to rationalize the use of imaging tests in patients with a clinical suspicion of PE. An algorithm based on helical CT has gained widespread interest due to the availability of helical CT. However, these algorithms have often been implemented without appropriate assessment in clinical practice. If one is to implement helical CT as a first line diagnostic test for patients with clinically suspected pulmonary embolism it is important to note that a) CT is sensitive to larger emboli b) single slice technology may miss smaller subsegmental pulmonary emboli and c) outcome studies using a combination of normal single slice helical CT and normal compression ultrasonography rules out safely pulmonary embolism. In view of recent developments in multi row detector CT technology, large, well-designed studies are needed to determine the exact role of multi row helical CT in diagnosing PE.