Many institutions are starting to see roll-out of some sort of clinical decision-support for imaging utilization. Whether it be NEXUS, Canadian Head CT, or Wells for PE, there is plenty of literature documenting improved yield following implementation.
This retrospective evaluation looks at what happens when you don’t obey your new robot overlords – and perform CTPA for pulmonary embolism outside the guideline-recommended pathway. These authors looked specifically at non-compliance at the low end – patients with a Wells score ≤4 and performed with either no D-dimer ordered or a normal D-dimer.
During their 1.5 year review period, there were 2,993 examinations and 589 fell out as non-compliant. Most – 563 – of these were low-risk by Wells and omitted the D-dimer. Yield for these was 4.4% positivity, compared with 11.2% for exams ordered following the guidelines. This is probably even a high-end estimate for yield, because this includes 8 (1.4%) patients who had subsegmental or indeterminate PEs but were ultimately anticoagulated, some of whom were undoubtedly false positives. Additionally, none of the 26 patients that were low-risk with a normal D-dimer were diagnosed with PE.
Now, the Wells criteria are just one tool to help reinforce gestalt for PE, and it is a simple rule that does not incorporate all the various factors with positive and negative likelihood ratios for PE. That said, this study should reinforce that low-risk patients should mostly be given the chance to avoid imaging, and a D-dimer can be used appropriately to rule-out PE in those where PE is a real, but unlikely, consideration.
“Yield of CT Pulmonary angiography in the emergency Department When Providers Override evidence-based clinical Decision support”
https://www.ncbi.nlm.nih.gov/pubmed/27689922