Pulmonary embolism during pregnancy: diagnosis with lung scintigraphy or CT angiography?

To evaluate the rate of positive, negative, and indeterminate results and the agreement between initial and expert readings for lung scintigraphy and computed tomographic (CT) angiography performed in patients suspected of having pulmonary embolism (PE) during pregnancy.

Institutional review board approval was obtained. The authors retrospectively analyzed the images from lung scintigraphy and CT angiography performed in pregnant patients during the past 9 years. Images from 46 CT angiographic examinations performed in 43 patients and 91 of 94 lung scintigraphic examinations were reviewed by experts, whose readings were then compared with the initial reports. For CT angiography, the quality of opacification was graded as good, suboptimal, or poor and intraarterial attenuation was measured.

The rates of positive findings (seven of 43 patients [16%] with CT angiography and 10 of 91 patients [11%] with scintigraphy, P = .36), negative findings (28 of 43 patients [65%] with CT angiography and 64 of 91 patients [70%] with scintigraphy, P = .54), and indeterminate findings (eight of 43 patients [19%] with CT angiography and 17 of 91 patients [19%] with scintigraphy, P = .99) were similar for CT angiography and lung scintigraphy. There were four discrepancies between initial and expert readings for CT angiography (κ = 0.84; confidence interval: 0.68, 0.99) and 14 for lung scintigraphy (κ = 0.75; 95% confidence interval: 0.63, 0.87). Opacification was classified as good for only 23 of the 46 CT angiographic examinations (50%). Attenuation values were significantly different among the groups with good, suboptimal, or poor opacification. Alternative diagnoses unsuspected at chest radiography were demonstrated at CT angiography in five of the 43 patients (12%). The mean maternal radiation dose was 0.9 mSv for lung scintigraphy and 7.3 mSv for CT angiography.

Lung scintigraphy and CT angiography have comparable performances for PE diagnosis during pregnancy. Interobserver agreement is better for CT angiography, which also enables alternative diagnosis of unsuspected disease but delivers higher maternal radiation dose.