A randomized trial of spiral CT and ventilation perfusion scintigraphy for the diagnosis of pulmonary embolism

Purpose: To compare spiral computed tomographic pulmonary angiography (SCTA) with lung ventilation-perfusion scintigraphy (VQS) as the initial investigation of patients with suspected pulmonary embolism (PE). Materials and Methods: Prospective randomized trial of 78 patients with suspected pulmonary embolism. Patients underwent either SCTA or lung VQS as their initial investigation for PE, Cross-over between groups meant that 50 patients received both examinations, The clinicians' assessment of overall clinical likelihood of PE was also collected. Results: (1) It was possible to make a confident diagnosis in a significantly larger proportion of patients when SCTA was used as the initial investigation (35/39, 90%) compared with using VQS first (21/39, 54% P < 0.001). The main difference between the two groups was that SCTA demonstrated lesions other than pulmonary embolism considered responsible for the patients' symptoms in 13/39 patients (33%) randomized to SCTA as the initial investigation and following a non-diagnostic VQS in 10/39 patients (25%) randomized to VQS as the initial investigation. (2) There was no difference in the prevalence or detection of PE in the two groups. SCTA demonstrated pulmonary emboli in 6/39 patients (16%) in the SCTA first group and VQS was high probability for PE in 5/39 patients (13%) in the VQS first group, SCTA detected PE in a further two patients in the VQS first group. Conclusion: It is proposed that, where logistically feasible, SCTA should replace VQS as the initial investigation for PE in patients with an underlying cardio-respiratory disorder.