Current diagnostic techniques for pulmonary embolism.

The diagnosis of venous thromboembolism (VTE) includes deep venous thrombosis (DVT) and pulmonary embolism (PE) and requires objective testing. The clinician uses a combination of risk factors and nonspecific clinical findings to identify patients who warrant such an evaluation. The recommended approach begins with ventilation/perfusion (V/Q) lung scans or lower extremity noninvasive studies by compression ultrasonography. Nondiagnostic V/Q scans or negative noninvasive studies require further testing. A high-probability V/Q scan or a positive noninvasive study warrant treatment. A normal V/Q scan excludes the diagnosis of PE. Helical computed tomography (CT) can diagnose PE of major vessels but is not sufficiently sensitive to exclude PE because of its poor sensitivity for subsegmental pulmonary vessels. Newer D-dimer assays have a high negative predictive value, but results vary with the specific assay and do not perform well in patients with cancer. Future studies are needed to validate magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA).