CT pulmonary angiography (CTPA) was not inferior to ventilation-perfusion scanning in ruling out pulmonary embolism. However, significantly more patients were diagnosed with pulmonary embolism using the CTPA approach, according to a study published in the Dec.19 issue of the Journal of American of Medical Association.
Ventilation-perfusion scanning has been largely replaced by CTPA in many centers despite limited comparative formal evaluations and concerns about CTPA's low sensitivity, or the chance of missing clinically important pulmonary embuli.
David R. Anderson, MD, of the Queen Elizabeth II Health Sciences Centre in Halifax, Nova Scotia, and colleagues, undertook the study to determine whether CTPA may be relied upon as a safe alternative to ventilation-perfusion scanning as the initial pulmonary imaging procedure for excluding the diagnosis of pulmonary embolism in acutely symptomatic patients.
The patients were randomized to undergo either ventilation-perfusion scanning or CTPA. Patients in whom pulmonary embolism was considered excluded did not receive antithrombotic therapy and were followed up for a three-month period.
The researchers said that the primary outcome was the subsequent development of symptomatic pulmonary embolism or proximal deep vein thrombosis in patients in whom pulmonary embolism had initially been excluded.
According to the study, 701 patients were randomized to CTPA and 716 to ventilation-perfusion scanning. Of these, 133 patients (19.2 percent) in the CTPA group compared to 101 (14.2 percent) in the ventilation-perfusion scan group were diagnosed as having pulmonary embolism in the initial evaluation period (difference of 5 percent) and were treated with anticoagulant therapy. Of those in whom pulmonary embolism was considered excluded, 2 of 561 patients (0.4 percent) randomized to CTPA compared to 6 of 611 patients (1 percent) undergoing ventilation-perfusion scanning developed venous thromboembolism in follow-up, including one patient with fatal pulmonary embolism in the ventilation-perfusion group.
The authors concluded that ventilation-perfusion lung scanning should still have a role to play for the investigation of pulmonary embolism because test involves much less radiation exposure and has fewer adverse effects and contraindications than CTPA.
However, Anderson and colleagues said that significantly more patients were diagnosed and treated for pulmonary embolism with CTPA than ventilation-perfusion scanning, and said that further research is required to determine whether all pulmonary emboli detected by CTPA should be managed with anticoagulant therapy.