Can CT pulmonary angiography replace ventilation-perfusion scans as a first line investigation for pulmonary emboli?
A prospective study was performed to determine efficacy of diagnosis of pulmonary emboli by computed tomographic pulmonary angiography (CTPA) in patients who underwent both CTPA and ventilation-perfusion (V/Q) scanning. The results were compared with the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study in which conventional pulmonary angiography had been performed instead of CTPA. Forty-two of 161 (26%) patients had a positive CTPA compared with a 27% prevalence in the PIOPED population. Fourteen of 16 patients (87.5%) with high-probability V/Q scans also had a positive CTPA compared with 87% in PIOPED. Twelve of 40 patients (30%) with intermediate probability V/Q scans also had a positive CTPA compared with 34.7% in PIOPED, while 12 of 80 patients (15%) who had low-probability V/Q scans had positive CTPA compared with 14.5% in PIOPED. Four of 25 patients (16%) with normal V/Q scans had positive CTPA compared with 0% in PIOPED. While the present study size was r
