Prospective Multi-Center Evaluation of the Pulmonary Embolism Rule Out Criteria
This 2008 study was the second large validation study of the Pulmonary Embolism Rule Out Criteria (PERC) rule. The researchers aimed to test the hypothesis that follows: patients who presented with signs and symptoms of PE but were estimated to be low risk by clinician gestalt (<15% pretest probability), in addition to being PERC negative, would have a <2% risk of VTE. Less than 2% was determined to be the point of equipose, where the dangers of workup for PE in this group (radiation exposure, incidentaloma findings) would be greater than the risk of actually finding a clinically significant PE.
Methodology and Design:
12 Large Emergency Departments in the US and 1 in New Zealand
8,138 Patients enrolled
Prospective cohort study
Patients were enrolled when a diagnostic test for PE was ordered in the ED (D-Dimer, CTA, V/Q Scan, CT Arteriography)
At time of diagnostic test ordering, clinician was asked to fill out a survey that included categorizing the patient as low (<15%), medium (15-40%), and high (>40%) risk of PE by gestalt. They also had to fill out the PERC rule.
Primary outcome –> did the patient have VTE at 45 day follow up? Did the patient die?
Patients were excluded if they had features deeming them at risk to be lost to follow up (serious mental illness, homeless, etc)
8,138 patients –> 513 found to have venous thromboembolism.
One death from PE (56 deaths not from VTE)
Low, medium, and high risk patients by gestalt had VTE at the following rates respectively: 3.5%, 10.4%, and 31.1%
PERC negative had a “sensitivity” (as in, no VTE was a positive result for a negative PERC) of 95.7%.
Patients with who were PERC negative AND deemed low risk by clinician result (aka very low risk) had VTE ~1%
PERC is a reliable tool in ruling out PE for patients deemed low risk by gestalt
Further diagnostic testing in these patients is more likely to be harmful than beneficial
There is still too much diagnostic testing being performed for low risk PE (1,843 normal CTPEs performed in this study alone! 362 of these were VERY LOW RISK patients)
Limitations and Discussion:
Generalization for our patient population at Temple (excluded any patients with potential loss for followup)
Did not discuss how many of these VTEs were clinically significant and complications of treating these VTEs. (heparin is not benign!)
What do we do with those who are low risk but PERC+? What about medium risk? Is there a role for ultrasound in ruling these out? Further work needs to be done.