DVT and pulmonary embolism: Part I. Diagnosis.

The incidence of venous thromboembolic diseases is increasing as the U.S. population ages. At least one established risk factor is present in approximately 75 percent of patients who develop these diseases. Hospitalized patients and nursing home residents account for one half of all cases of deep venous thrombosis. A well-validated clinical prediction rule can be used for risk stratification of patients with suspected deep venous thrombosis. Used in combination with D-dimer or Doppler ultrasound tests, the prediction rule can reduce the need for contrast venography, as well as the likelihood of false-positive or false-negative test results. The inclusion of helical computed tomographic venography (i.e., a below-the-pelvis component) in pulmonary embolism protocols remains under evaluation. Specific combinations of a clinical prediction rule, ventilation-perfusion scanning, and D-dimer testing can rule out pulmonary embolism without an invasive or expensive investigation. A clinical prediction rule for pulmonary embolism is most helpful when it is used with subsequent evaluations such as ventilation-perfusion scanning, D-dimer testing, or computed tomography. Technologic advances are improving the resolution of helical computed tomography to allow detection of smaller emboli; however, further study is needed to provide definitive evidence supporting the role of this imaging technique in the diagnosis of pulmonary embolism. D-dimer testing is helpful clinically only when the result is negative. A negative D-dimer test can be used in combination with a clinical decision rule, ventilation-perfusion scanning, and/or helical computed tomography to lower the probability of pulmonary embolism to the point that aggressive treatment is not required. Evidence-based algorithms help guide the diagnosis of deep venous thrombosis and pulmonary embolism.