The prevalence of PE in patients with syncope may be far less that the PESIT trial indicated: 1.4% vs. 17%.
Why does this matter?
The PESIT trial earlier this year found that 1 in 6 patients admitted with syncope were found to have PE. This just didn't seem to mesh with reality for most of us. So this small study took a stab at getting to the real prevalence of PE in syncope patients, though it is pretty low quality evidence.
PE workup gone wild
This was a retrospective review of 348 patients presenting to the ED with syncope over a 5.5 year period. They found, "The overall rate of PE among patients presenting to the ED with syncope was 1.4%." That is substantially lower than PESIT, at 17%. In reality, there were only 2 PEs diagnosed in the ED; the other 3 were discovered by phone follow up, could not be confirmed, and all had pretty sketchy stories. So the prevalence of PE may have been as low as 0.5%. The study was severely limited by its retrospective design, the fact that not all patients got a PE workup, and that they were unable to contact 30% of patients by phone follow up. So we really don't know if some patients admitted for PE actually had it but they just didn't look or if they had subsequent PE but they just didn't find out. The question is, do patients without other symptoms to indicate PE need a PE workup? This was the beef with PESIT. We don't check rectal tone on patients with ankle sprains. It seems just as excessive to workup PE in every patient admitted for syncope.
Prevalence of pulmonary embolism in patients presenting to the emergency department with syncope. Am J Emerg Med. 2017 Jul 31. pii: S0735-6757(17)30639-3. doi: 10.1016/j.ajem.2017.07.090. [Epub ahead of print]
See Radecki's take on this and some great discussion in the comments.