PERC? ...What?!

Remember me?

This confused the crap out of me, and apparently I'm not the only one.
Pulmonary Embolisms are scary, the presentation is highly variable but the test for diagnosis comes with a high dose of radiation. That being said, the D-Dimer is the first line of defense in diagnosing PE, but isn't very specific.




The Pulmonary Embolism Rule-out Criteria was designed by some very smart people in 2004 to help justify NOT getting a D-Dimer in low and very low risk groups. The goal is if the patient meets ALL of the 8 criteria listed, and is in the low/very low risk group. THEN you can justify NOT getting the D-Dimer.

1. < 50 y/o
2. HR < 100
3.SpO2 > 94% RA
4. No H/O DVT/PE
5. No recent surgery
6. No hemoptysis
7. No exogenous estrogen (i.e. birth control)
8. No clinical signs suggesting DVT

Now for the hard part; this only applies if the pre-test probability is LESS or equal to 15%. This is where gestalt takes over, it's up to YOU as the provider to decide what the risk of a PE is. If you feel it is less than 15%, then apply PERC and call it a day. If you risk stratify and feel it is higher, then I would get the D-Dimer and go from there. Scott Weingart provides a nice algorithm if you are a visual learner.





What is the low risk group?
Essentially these are the people who do NOT have the classic complaints that make PE suspicious:
-NO C.C. of shortness of breath, syncope, pleuritic chest pain, substernal chest pain
-NO H/O cancer/malignancy
-NO H/O thrombophilia
-NO H/O smoking
-NOT postpartum



Life in the Fast Lane also provides a great review on the topic.

References:
Kline JA, et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost 2004; 2: 1247–55.

Kline JA, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost 2008; 6: 772–80. (PMID: 18318689).