New in EM 004: PoCUS in diagnosing the cause of SOB in the ED

19 Apr

Originally Published on RCEM Learning Podcast May 2017

As part of the RCEM Learning Podcast I record reviews of recent literature with Dave McCreary. We’ve been doing this for about a year now and you can hear them all on the RCEM Learning Podcast each month. I’d like to have them here and searchable on this site too so I’ll be posting the ones I find most relevant here. You can hear the newest ones by subscribing to the free RCEM Learning Podcast. 

Audio:

Clinical Question:

  • How useful is PoCUS in diagnosing the cause of SOB in the ED

Title of Paper:

Journal

  • Chest 2017

Author

  • Maurizio Zanobetti

Background

  • SOB is a common presenting complaint and particularly when it comes to diagnosing heart failure vs penumonia (two of the commonest causes) then the typical ED work up is imperfect
  • Thoracic PoCUS has gained lots of traction, especially for heart failure but is PoCUS accurate in diagnosing other causes of SOB

Patients studied

  • ED patients in Italy over a year presenting with undifferentiated SOB. Only included if they ultimately got admitted so obviously this is a sicker cohort than most.
  • They had a clinical assessment by an EP and an ECG. At this point the patient also got a structured PoCUS by an EP sonographer (who was well trained and experienced it seems). Based on the clinical assessment and PoCUS, the doc who did the PoCUS had to name his diagnosis. The doctor responsible for the patient could then order his usual work up and once that was completed he had to name his diagnosis.
  • The gold standard here was final diagnosis with every bit of available info obtained during the patient’s stay (unclear if the PoCUS formed part of this – incorporation bias a risk here). This final diangosis was decided by 2 EPs reviewing all this data. This isn’t an ideal gold standard by any means but it is the usual standard used in heart failure studies.

Study Type

  • This is an observational diagnostic study. Which means you need to look for the index test (the one under investigation) and the reference standard (the gold standard)
  • There are actually 2 index tests here
    • First is the diagnosis made by the doc doing the PoCUS
    • Second is the diagnosis made by the treating doc after the full ED work up
  • The reference test here is the final diagnosis by the 2 EPs with all the data
  • There was no clear statement of primary outcome here but it seems to be the diagnostic characteristics of ED diagnosis and PoCUS diagnosis

Results

  • 2700 pts
  • in terms of the frequency of final diagnosis it was pneumonia (35%), COPD/asthma (25%) and CHF (20%) with a smattering of others in the list
  • PoCUS wins at heart failure and is equivalent at pneumonia. Not so much for the others.
  • The eye catching bit of the paper is table 4 which collects all the diagnostic characteristics for each different diagnosis. The LR presented here are a little crazy
    • PoCUS for heart failure +LR = 21, for ACS 105, for PE 350
    • I have a few issues with these first of which being the question – was the PoCUS part of the reference standard – if so then it’s not surprising that it comes out great. Second, these just don’t pass sniff test for me – there’s a recent systematic review in Acad EM that found b lines to have the best characteristics for diagnosing heart failure but still only around a +LR of 8

Thoughts

  • For heart failure this is increasingly becoming a well tested investigation that we should get well trained in
  • Similar things can be said for penumonia but there’s definitely a steeper learning curve
  • As for all things PoCUS, a lot of it is new, and while its increasingly evidence based, you still have to do the work and get as much practice and training and reading as you can.

Kudos

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