Laboratory markers in the diagnosis of venous thromboembolism.

Selected blood tests may be useful in the diagnosis of venous thromboembolism (VTE), or in the identification of a congenital or acquired defect associated with the development of VTE. Several studies have shown the D-dimer assay to have a high negative predictive value but poor specificity when used in the detection of VTE. Yet in the emergency room setting, the D-dimer test may be useful if a detailed risk factor analysis for each patient is included in the diagnosis. The presence of such genetic thrombophilia markers as factor V Leiden, prothrombin 20210A mutation, and antiphospholipid antibodies significantly increases a patient's risk of a thrombotic event. The relative risk of thrombosis in factor V heterozygotes is at least 3 times higher than in the general population, whereas the increased risk of thrombosis in homozygotes is estimated to be 50- to 80-fold greater than those without the defect. Thromboembolic events are reported in approximately one third of antiphospholipid-positive patients. Other markers such as hyperhomocysteinemia and deficiencies of antithrombin, protein C, or protein S, when combined with the previous mutations, significantly increase a patient's risk of a thrombotic event. We feel that it is important to identify these ultra-high-risk patients to provide adequate counseling about the risk of thrombosis before elective surgical procedures. Often, lifelong anticoagulation may be needed as these patients and family members may need testing before taking birth control pills or hormonal replacement.

Thrombosis prophylaxis in orthopedic surgery: current clinical considerations.

Thrombosis prophylaxis in orthopedic surgery is an important consideration in order to avoid the morbidity and mortality of venous thromboembolism (VTE). Patients who do not receive prophylaxis, or receive inadequate prophylaxis, may be at risk for clinical or fatal pulmonary emboli, and a fatality, although rare, may be the first sign of a VTE. Although the surgeon may have corrected the patient's orthopedic problem, a symptomatic or asymptomatic venous thrombosis may become a new threat to the patient's quality of life. This problem places such patients at risk for recurrent VTE, as well as post-thrombotic syndrome, a progressive, lifelong disability. Methods of prophylaxis that prevent the most clots result in the fewest venous thromboembolic events, but no one method of prophylaxis is suitable for all patients. In order to select the appropriate modality, a careful risk assessment of each patient is necessary. Those at low or moderate risk levels do not require the same modalities that may be used in a patient with a previous history of thrombosis or with many risk factors. The purpose of this brief review is to examine the complications associated with venous thromboembolism and to discuss, in detail, the risk of thrombosis in orthopedic patients. In addition, thrombosis prophylaxis modalities are discussed and suggestions made based on current Chest Consensus Guidelines and FDA-approved products.