Myth 1: CTPA Is the Incontrovertible Standard for PE
Today’s imaging standard for pulmonary embolism (PE) is CT pulmonary angiogram (CTPA). However, in the context of overinvestigation leading to overdiagnosis, we must recognize the limitations of CTPA. Conventional wisdom and recent evidence have informed us that without proper risk stratification for low-risk patients, PE is pursued when it should not be. Just with shopping, when you look, you find, and when you find, you buy. With CTPA, when we look, we find, and when we find, we treat. Thus, we know we need to be looking less often.
Conventional wisdom has also led us to the practical question of whether all diagnosed PEs (especially isolated subsegmental PEs) are clinically relevant and worthy of anticoagulation. However, Hutchinson et al have taken this discussion to a new level.1 They set aside the concept of clinical relevance to answer the question of whether such radiographic PEs are truly PEs at all.
The authors performed a retrospective review of 174 patients with CTPAs positive for PE. They performed blinded reviews of these studies by chest radiologists, comparing them to initial readings by general radiologists. The overall discordance rate was 25.9 percent. In other words, one-quarter of the PEs diagnosed on CTPA were overinterpretations and not even radiographic PEs. When the discordance rate was broken down further, the story gets even better. For solitary PEs, the discordance rate was 46.2 percent, but for multiple PEs, it was 13.1 percent. This implies that an interpretation of a solitary PE is more likely to be in error than one reporting multiple PEs. Segmental PEs and subsegmental PEs had respective discordance rates of 26.8 percent and 59.4 percent, and finally, with interpretations of lower-lobe solitary subsegmental PEs, the experts disagreed with the initial interpretations 66.7 percent of the time. The causes cited for overinterpretation were 24 from motion artifact, 10 from beam hardening artifact, and eight from poor contrast opacification.| | | Next → | Single Page