Seminars in thrombosis and hemostasis
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Conventional pulmonary arteriography for the diagnosis of pulmonary embolism (PE) bears several limitations in clinical practice, basically due to its invasiveness. On the other hand, no single noninvasive test is both sensitive and specific for the diagnosis of PE. Therefore, the choice of available noninvasive diagnostic tests guided by the clinical probability of PE is a good compromise at present. ⋯ Therefore, spiral CT should not be used as a primary tool for the diagnosis of PE; its role needs to be re-evaluated in light of its sensitivity, feasibility, and radiation burden on the patients. In patients in whom the diagnosis of PE cannot be made at the end of the noninvasive pathway, the use of the invasive techniques must be taken into consideration. In our experience, however, such cases should not exceed 15 to 20% of the total patient population.
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Patients with clinical conditions such as surgery, trauma, and acute medical illness have a transiently increased risk of venous thromboembolism and merit consideration for adequate thromboprophylaxis. The choice of an appropriate pharmacologic or physical means of prophylaxis should be made taking into account both the thrombotic and bleeding risk associated with patient-related factors and the type of surgery or other disease state involved. A large number of randomized clinical trials, meta-analyses, and guidelines developed by scientific societies worldwide have addressed this issue and have provided information and recommendations that should be considered carefully. ⋯ Patients at moderate thrombotic risk face a 10 to 20% risk of deep vein thrombosis (DVT) and require prophylaxis with low-dose unfractionated heparin or low molecular weight heparins (LMWHs) at a dosage < 3400 U once daily, or with graduated elastic stockings if their bleeding risk is high. Patients with an expected 20 to 40% DVT rate without prophylaxis are considered at high thrombotic risk and should be treated preferentially with LMWHs at high prophylactic dosage (> 3400 U). Patients undergoing major orthopedic surgery face a DVT rate > 40%, are considered at very high risk of venous thromboembolism, and should be given either LMWHs at high prophylactic dosage, fondaparinux, or vitamin K antagonists--either alone or in association with intermittent pneumatic compression devices.
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Semin. Thromb. Hemost. · Oct 2006
Review Comparative StudyDifferent accuracies of rapid enzyme-linked immunosorbent, turbidimetric, and agglutination D-dimer assays for thrombosis exclusion: impact on diagnostic work-ups of outpatients with suspected deep vein thrombosis and pulmonary embolism.
The requirement for a safe diagnostic strategy should be based on an overall posttest incidence of venous thromboembolism (VTE) of less than 1%, with a negative predictive value of more than 99 to 100% during 3-month follow-up. Compression ultrasonography (CUS) and spiral computed tomography (CT) currently are the methods of choice to confirm or rule out deep venous thrombosis (DVT) and pulmonary embolism (PE), respectively. CUS has a negative predictive value (NPV) of 97 to 98%, indicating the need to improve the diagnostic work-up of patients with suspected DVT by clinical score assessment and D-dimer testing. ⋯ The rapid quantitative and qualitative agglutination D-dimer assays for the exclusion of VTE are not sensitive enough as stand-alone tests and should be used in combination with clinical score assessment. A normal rapid ELISA VIDAS D-dimer test as a stand-alone test safely excludes DVT and PE, with a NPV of 99 to 100%, irrespective of clinical score, without the need of CUS or spiral CT. The combined strategy of a rapid ELISA VIDAS D-dimer followed by objective testing with CUS for DVT and by spiral CT for PE will reduce the need for noninvasive imaging techniques by 40 to 50%.
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About 10% of all episodes of venous thrombosis are due to upper extremity deep vein thrombosis (UEDVT). Associated risk factors are indwelling central venous catheters, cancer, and coagulation defects; 20% of the episodes are unexplained. The onset of UEDVT is usually heralded by complaints such as arm swelling and pain, but may also be completely asymptomatic, especially in carriers of central venous lines. ⋯ Unfractionated or low molecular weight heparins followed by oral anticoagulants should be regarded as the treatment of choice, whereas thrombolysis and surgery may be indicated in selected cases. Up to one third of the patients develop pulmonary embolism that may be fatal; postthrombotic syndrome and recurrent thromboembolism are also frequent complications. UEDVT should no longer be regarded as a rare and benign disease, as reported previously.
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Semin. Thromb. Hemost. · Sep 2006
Review Comparative StudyComparative analysis and classification of von Willebrand factor/factor VIII concentrates: impact on treatment of patients with von Willebrand disease.
von Willebrand disease (vWD) is a bleeding disorder that results from defects in the quality or quantity of von Willebrand factor (vWF), a glycoprotein essential for normal thrombus formation. vWF circulates in plasma as multimers in sizes ranging up to 20,000 kd. The high molecular weight vWF (HMWvWF) multimers are most essential for primary hemostasis, whereas the lower molecular weight multimers are less functionally active. For many patients, the treatment of choice is factor replacement with a vWF/FVIII concentrate, preferably one with a high content of HMWvWF multimers. ⋯ Of the products tested, Haemate P/Humate-P had the highest content of HMWvWF multimers (with a multimer pattern closest to that of normal human plasma), the highest specific vWF activities, and the highest values of vWF:RCo and vWF:CB per unit of FVIII:coagulant (C). The goal of bleeding prophylaxis and treatment in type 2, severe type 1, and type 3 vWD patients is to normalize vWF activities (vWF:RCo and vWF:CB) and FVIII:C preferentially by vWF/FVIII concentrates containing the high vWF multimers and a high vWF:RCo/FVIII ratio to achieve normal primary and secondary hemostasis. Based on the present study of a comparative analysis of currently available vWF/FVIII concentrates, a classification of vWF/FVIII products is proposed.