By Dr. Geoffrey Modest
The Clinical Guidelines Committee of the Am College of Physicians published a paper detailing what they consider to be “best practice advice” for the evaluation of patients with suspected acute pulmonary embolism –PE– (see doi:10.7326/M14-1772), focusing on what they see as the overuse of CT scans and plasma D-dimer tests.
Their advice:
- Use validated clinical prediction rules to estimate the pretest probability of PE (e.g. Wells prediction rules or revised Geneva score, included below)
- Patients who have low pretest probability of PE and who also meet all of the Pulmonary Embolism Rule-Out Criteria (PERC, included below) should NOT have a D-dimer done
- Patients with an intermediate pretest probability of PE, or low pretest probability but do not meet all of the PERC, should have a high-sensitivity D-dimer done
- In patients over 50yo, use age-adjusted D-dimer thresholds (agex10ng/ml, rather than a universal cutoff of 500 ng/ml)
- In those with D-dimer levels below the above threshold, do NOT do any imaging (studies show way too many are done in ERs with no improvement in patient outcomes, though lots of radiation exposure and expense (see https://stg-blogs.bmj.com/bmjebmspotlight/category/radiation/for more reviews on excesses of radiation exposure)
- In patients with high pretest probability of PE, go directly to CTPA (CT pulmonary angiography). Use ventilation-perfusion scans only if contraindication to CTPA or CTPA not available. Do NOT get D-dimer in addition
A few supportive points:
- D-dimer has low specificity, but a normal high-sensitivity D-dimer in recent studies had a 99.5-100% sensitivity for excluding PE on CT scan
- The PERC (which is not a screening tool for all patients but only those with signs/symptoms potentially suggestive of PE) in a large meta-analysis has found that the overall proportion of missed PEs was 0.3%, with pooled sensitivity of 97%. In those with score of “0”, they state “the risk for PE is lower than the risks of testing”
- Of note, pregnancy, heart failure or stroke are not part of the Geneva score because they do NOT add to its predictive performance
- They do stress that alternative approaches may be okay: e.g., if someone has concerns for PE, are hemodynamically stable, and have lower extremity symptoms, it is reasonable to get leg ultrasound, and anticoagulate if positive (i.e., spare the radiation exposure, since the patient will be treated anyway). Though one issue is length of therapy here. Those who get a PE are at higher risk for a recurrent PE than those who just have a DVT. They comment that for patients with “cardiothoracic symptoms, the need for long-term anticoagulation can be determined after the initial treatment period”. I’m not sure what that means exactly. As I have mentioned in previous blogs, there are some interesting data supporting either checking D-dimer levels before stopping therapy or 3-4 weeks after stopping it (I actually do both), and in those with normal D-dimers one can stop therapy (this is not accepted universally as strategy, in part because those with normal D-dimers can still get PEs, though the studies suggest they are much less likely. I do discuss the risks and benefits of stopping anticoagulation with patients and try to make a joint strategy) — See https://stg-blogs.bmj.com/bmjebmspotlight/category/vte/ for more detailed articles/critiques.
Wells prediction rules:
Revised Geneva score:
PERC:
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