A critical appraisal of non-invasive diagnosis and exclusion of deep vein thrombosis and pulmonary embolism in outpatients with suspected deep vein thrombosis or pulmonary embolism: how many tests do we need?

The requirement for a safe diagnostic strategy should be based on an overall posttest incidence of venous thromboembolism of less than 1% during 3 month follow-up. Compression ultrasonography (CUS) has a negative predictive value (NPV) of 97% to 98% indicating the need of repeated CUS testing. Serial CUS testing is safe but you have to repeat 100 CUS to find 1 or 2 CUS positive for deep vein thrombosis (DVT), which is not cost-effective indicating the need to improve the diagnostic work-up of DVT by the use of clinical score assessment and D-dimer testing. The combination of a less sensitive D-dimer test (SimpliRed) and low clinical score does not, whereas the combination of a sensitive D-dimer test (ELISA VIDAS or Tinaquant) and low clinical score does safely exclude DVT without the need of CUS. The combination of a first negative CUS and a negative less sensitive D-dimer test (SimpliRed) or a sensitive ELISA D-dimer at a higher cut off level of 1,000 ng/ml safely excludes DVT with a NPV of > 99% without the need to repeated CUS in about 60%. The sequential use of a sensitive D-dimer and clinical score assessment will safely reduce the need for CUS testing by 40% to 60%. Large prospective outcome studies demonstrate that one negative examination with complete duplex color ultrasonography (CCUS) of the proximal and distal veins of the affected leg with suspected DVT is safe to withhold anticoagulant treatment with a NPV of 99.5%. This indicates that CCUS is equal or superior to serial CUS or the combined use of clinical score, D-dimer testing and CUS. Pulmonary angiography is the gold standard for segmental pulmonary embolism (PE) but not for subsegmental PE. A normal perfusion lung scan and a normal rapid ELISA VIDAS D-dimer test safely exclude PE. Helical spiral CT detects all clinically relevant PE and a large number of alternative diagnoses in symptomatic patients with a non-diagnostic ventilation perfusion scan (VP-scan) or a high probability VP-scan. Single-slice helical CT as the primary diagnostic test in patients with suspected PE in 5 retrospective studies and in 3 prospective management studies indicate that the NPV of a normal helical spiral CT, a negative CUS of the legs together with a low or intermediate pretest clinical probability is 99%. Helical spiral CT can replace both the VP-scan and pulmonary angiography to safely rule in and out PE. The combination of clinical assessment, a rapid ELISA VIDAS D-dimer followed by CUS will reduce the need for helical spiral CT by 40% to 50%.