Pulmonary embolism diagnosis and mortality with pulmonary CT angiography versus ventilation-perfusion scintigraphy: evidence of overdiagnosis with CT?

OBJECTIVE: The purposes of this study were to determine whether pulmonary emboli diagnosed with pulmonary CT angiography (CTA) represent a milder disease spectrum than those diagnosed with ventilation-perfusion (V/Q) scintigraphy, to determine the trends in incidence and mortality among patients with the diagnosis of pulmonary embolism from 2000 to 2007, and to correlate incidence and mortality trends with imaging modality trends.

MATERIALS AND METHODS: Diagnoses of pulmonary embolism from 2000 to 2007 at an urban academic medical center were retrospectively identified. Patient data were collected from the hospital database and the Social Security Death Index. Incident diagnoses, type of imaging used, and date of death were documented. Bivariate and multivariate analyses were used to explore the relations between imaging use and the incidence and mortality of pulmonary embolism. Logistic regression analysis was used to estimate the odds of death of pulmonary embolism diagnosed with pulmonary CTA versus V/Q scintigraphy.

RESULTS: The cases of 2087 patients (1361 women, 726 men; mean age, 61.8 years) with pulmonary embolism were identified. From 2000 to 2007 the incidence of pulmonary embolism increased from 0.69 to 0.91 per 100 admissions in strong correlation with increased use of pulmonary CTA. There was no change in mortality, but the case-fatality rate decreased from 5.7% to 3.3%. On average, pulmonary emboli diagnosed with pulmonary CTA were one half as lethal as those diagnosed with V/Q scintigraphy (odds ratio, 0.538; 95% CI, 0.314-0.921).

CONCLUSION: The results of this study are evidence that the shift in imaging from V/Q scintigraphy to pulmonary CTA resulted in increased diagnosis of a less fatal spectrum of pulmonary embolic disease, raising the possibility of overdiagnosis. Outcome-based clinical trials with long-term follow-up would be helpful to further guide management.