We all love to hate PE. We can’t seem to stop discussing it or publishing papers on it and there’s even a whole conference just on VTE. We have a similar love hate relationship with the dimer. It’s useful to use when it’s negative (cause we already knew the patient didn’t have a PE…) but it gives us sweats when it’s falsely positive on the patient with minimal symptoms who we never should have ordered it on in the first place.
We are in a position where we know we are both underdiagnosing PE in certain patients and overdiagnosing it in lots of others.
There are 2 new diagnostic strategies available to us.
One involves adjusting the normal level of d dimer based on age and the other modifies the dimer cut off based on clinical probability.
Both strategies apply to the low/intermediate risk patients. High risk patients should be going straight to CT and shocked/hypotensive patients should be trying to get to CT if you can make it and considering lysis. We do OK with this population already and let’s face it they’re not that common.
This has been around for a while. I did my CTR for the FRCEM on the topic. The data is all observational and of variable quality
The Righini paper is the big one here.
There is of course a false negative rate – you will miss a very occasional patient by using this strategy. however you will also miss PE with using a convention strategy. In the Righini paper it was 0.1 v 0.3
The major limitation here is that it only applies to the over 50s if you’re 35 your cut off is still 500 in this protocol. if you’re 85 then your cut off is 850 but it’s hard to see the downside of doing a CT on an 85 year old. The contrast nephropathy probably is non existent and the chance of serious pathology (PE or otherwise) is so much higher in this group.
So at its most basic the AADD reduces testing in people who i’m not in a rush to reduce testing in.
It has recently been endorsed by ACEP in their updated VTE policy so you now have a guideline to back you up (it is not as yet endorsed by ACCP or the ESC guidelines)
All studies seem to make some horrifically forced acronym out of the title. (PARAMEDIC2 is a good example…) This one is apparently the YEARS study. Though I didn’t see them even make any attempt to explain where the YEARS came from. I suggested this…
They modify the Wells criteria to just 3 questions.
Your d dimer cut off is therefore dependant on your clinical risk.
My big concern with this paper is that the d dimer was done at triage before the assessing doctor answered the 3 questions. You can imagine that knowing the result of the dimer might change how you assign your pre test probability. Say you have a young female with a dimer of 950 and score negative on the other 2 questions of the YEARS protocol. The question “Is PE the most likely diagnosis” could be easily swayed by that knowledge.
Honestly i think either are reasonable to use, certainly as part of a departmental protocol you’d be well supported. I think they’re both similar in terms of their evidence base and they both provide safe and modest reductions in current imaging levels.
This is an obvious question and the age adjusted dimer is jsut starting to be studied for this. So far it seems the reduction in imaging is even more modest and given the limited harm in just doing it yourself or getting a formal ultrasound then I can’t see it being great benefit.
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