MDCT makes ultrasound unnecessary when testing for pulmonary embolism

The strategy combining D-dimer measurement and multi-detector CT (MDCT) is as safe as the strategy using D-dimer followed by venous compression ultrasonography of the leg and MDCT for exclusion of pulmonary embolism, according to a randomized controlled trial (RCT) published in the April 19 issue of the Lancet.

MDCT combined with D-dimer measurement can safely exclude pulmonary embolism in patients with a low or intermediate clinical probability of this disease, the authors noted.

Marc Righini, MD, from the department of internal medicine at the Geneva University Hospital in Geneva, Switzerland, and colleagues compared this combination with a strategy in which both a negative venous ultrasonography of the leg and MDCT were needed to exclude pulmonary embolism.

The researchers included 1,819 consecutive outpatients with clinically suspected pulmonary embolism in a multicenter non-inferiority RCT comparing two strategies: clinical probability assessment and either D-dimer measurement and MDCT (DD-CT strategy for 903 patients) or D-dimer measurement, venous compression ultrasonography of the leg, and MDCT (DD-US-CT strategy for 916 patients).

The primary outcome was the three-month thromboembolic risk in patients who were left untreated on the basis of the exclusion of pulmonary embolism by diagnostic strategy, according to the investigators.

Righini and colleagues found the prevalence of pulmonary embolism was 20.6 percent in both groups (189 cases in DD-US-CT group and 186 in DD-CT group). The researchers analyzed 855 patients in the DD-US-CT group and 838 in the DD-CT group per protocol.

The authors wrote that the three-month thromboembolic risk was 0.3 percentin the DD-US-CT group and 0.3 percent in the DD-CT group (difference of 0.0 percent). In the DD-US-CT group, ultrasonography showed a deep-venous thrombosis in 53 of 574 patients (9 percent), and thus MDCT was not undertaken.

The researchers found that the MDCT makes an ultrasound of the leg unnecessary when determining the presence of a pulmonary embolism. However, the researchers concluded that an ultrasound could be of use in patients with a contraindication to CT.

Swiss National Research Foundation, Projets Hospitaliers de Recherche Clinique and the Pneumologie Développement funded the trial.