Overdiagnosis of pulmonary embolism by pulmonary CT angiography

OBJECTIVE. The purpose of this study is to evaluate the rate of overdiagnosis of pulmonary embolism (PE) by pulmonary CT angiography (CTA) in a tertiary-care university hospital. MATERIALS AND METHODS. This study is a retrospective review of all pulmonary CTA examinations performed in a tertiary-care university hospital over a 12-month period. Studies originally reported as positive for PE were retrospectively reinterpreted by three subspecialty chest radiologists with more than 10 years' experience. A pulmonary CTA was considered negative for PE when all three chest radiologists were in agreement that the pulmonary CTA study was negative for PE. The location and potential causes for PE overdiagnosis were recorded. RESULTS. A total of 937 pulmonary CTA studies were performed over the study period. PE was diagnosed in the initial report in 174 of these cases (18.6%). There was discordance between the chest radiologists and the original radiologist in 45 of 174 (25.9%) cases. Discordance occurred more often where the original reported PE was solitary (46.2% of reported solitary PEs were considered negative on retrospective review) and located in a segmental or subsegmental pulmonary artery (26.8% of segmental and 59.4% of subsegmental PE diagnoses were considered negative on retrospective review). The most common cause of diagnostic difficulty was breathing motion artifact, followed by beam-hardening artifact. CONCLUSION. In routine clinical practice, PEs diagnosed by pulmonary CTA are frequently overdiagnosed, when compared with the consensus opinion of a panel of expert chest radiologists. Improvements in the quality of pulmonary CTA examination and increased familiarity with potential diagnostic pitfalls in pulmonary CTA are recommended to minimize misdiagnosis of PE.