Does your patient really need another chest CT?

Originally published in Journal Watch Emergency Medicine

by Richard D. Zane, MD, FAAEM

Repeat chest CT angiography scans have a low yield for diagnosing pulmonary embolism.

Computed tomography (CT) angiography of the chest is considered the definitive test for pulmonary embolism (PE) in the emergency department. Although CT angiography is readily available, it exposes patients to ionizing radiation and iodinated contrast dye (JW Emerg Med Aug 3 2007). In a prospective study of 675 ED patients who underwent chest CT angiography for the work-up of PE, researchers assessed rates of repeat chest CT angiography.

During 5 years of follow-up, 33% of patients underwent repeat chest CT angiography. Of the patients who underwent repeat testing, 22% were women younger than 40. Overall, 5.3% of index scans were positive for PE, compared with 3.4% of subsequent scans.

Comment: The rate of CT scanning in the ED is increasing every year, and we have yet to experience the downstream effect of the enormous societal exposure to radiation. The rate of positive repeat CT scans in this study was low (3.4%), but whether these tests were inappropriate, given the potential gravity of the disease, is not clear. Editorialists note that prospectively validated clinical decision algorithms have been shown to be accurate and reliable for predicting patients who might benefit from CT angiography (JW Emerg Med Mar 28 2006 and JW Emerg Med Feb 2 2005). Clinicians should strongly consider incorporating such algorithms into practice to minimize unnecessary scans, as more scrutiny is placed on the utilization of CT in emergency medicine.


Kline JA et al. Incidence and predictors of repeated computed tomographic pulmonary angiography in emergency department patients. Ann Emerg Med 2009 Jul; 54:41.

Piazza G and Goldhaber SZ. Chest computed tomography in the emergency department for suspected pulmonary embolism: It’s time to practice what we preach. Ann Emerg Med 2009 Jul; 54:49.

Copyright © 2009. Massachusetts Medical Society. All rights reserved.

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