Apparently, as many as one-third of them!
This is a retrospective study from a Spanish hospital evaluating all patients presenting through the Emergency Department who subsequently received a chest CTA revealing pulmonary embolism. These diagnoses were further classified as having received the diagnosis of PE on initial presentation, during hospitalization, or on a return visit to the Emergency Department. 66% of patients diagnosed with PE were diagnosed on the initial visit, while 22% were diagnosed only after hospital admission, and 12% on Emergency Department revisit. This leads to the authors conclusions that delayed diagnosis of acute PE is frequent despite current diagnostic strategies.
While it’s only a single center study, and the frequency of missed diagnoses may not be generalizable, it’s still a reasonable investigation. The characteristics of patients with missed PE fit the typical spectrum from other, prior studies: confounding comorbidities and diagnostic findings. Patients with delayed diagnosis had fewer typical features, were more likely to have COPD or asthma, more likely to have fever, and more likely to have pulmonary infiltrates. The authors state there were no mortality differences between early and delayed PE diagnosis, but the study is too small and heterogenous to truly put much faith in this observation. Of note, 41% of patients who were initially discharged from the ED had unilateral subsegmental clot, a far greater proportion than either other diagnostic group.
It certainly makes sense that patients with dyspnea and other potential causes will have their diagnosis delayed until their lack of response to therapy results in reassessment. These authors suggest we ought to be more aggressive in our evaluation for PE in the Emergency Department; I tend to feel the delayed diagnosis in confounding situations is appropriate, and suspect some of these represent subclinical disease. “Zero-miss” is only appropriate if the harms from the disease outweigh the harms of testing and treatment – and follow-up re-evaluation or additional testing during acute hospitalization are reasonable pathways to diagnosis in a subset of patients.
“Clinical features of patients inappropriately undiagnosed of pulmonary embolism”
http://www.ncbi.nlm.nih.gov/pubmed/24060320