[The SBU on prevention, diagnosis and treatment of thrombosis: New methods critically scrutinized]

Venous thromboembolism (VTE) causes more than 1,000 deaths and leads to the admission to hospital of 11,000 patients each year in Sweden. Prevention of venous thrombosis and pulmonary embolism is therefore of great importance. Diagnosis is difficult as the symptom profile is diffuse and difficult to interpret. Acute treatment and secondary prophylaxis are complicated as the risk of severe bleeding is great. A systematic review was carried out of the literature on prevention, diagnosis and treatment of VTE. Only randomized controlled studies were included and, to assess diagnostic methods, only studies with an independent comparison with a known reference method. Approximately 1,300 scientific studies met the requirements for high scientific quality. The scientific evidence strongly suggests that low molecular weight heparin can replace unfractionated heparin in preventing and treating venous thrombosis and pulmonary embolism. Treatment with a single daily injection, rather than two, of low molecular weight heparin yields equally favorable effects. The risk for hemorrhage is lower with low molecular weight heparin and management is simpler, which facilitates outpatient treatment. Longer-term secondary prophylaxis with warfarin reduces the risk for relapse, but several years of treatment also increases the risk for severe hemorrhage. The presence of treatment-demanding VTE can be excluded in outpatients by combining the assessment of clinical probability, using clinical decision rules, with measurement of D-dimer. Thorough ultrasonic examination of the leg and a CT scan of the pulmonary vessels usually provide sufficient diagnostic reliability, which strongly supports the use of these methods in clinical practice. It is not meaningful to conduct extensive investigations of patients with venous thrombosis to find possible underlying cancer. It is essential to develop more cost-effective methods to investigate genetic predisposition for thrombosis.