by Stacey Chamberlain
A 19-year-old female presents with sharp right flank pain and shortness of breath that started suddenly the day prior to arrival. The pain is worse with deep inspiration but not related to exertion and not relieved with ibuprofen. She denies anterior chest pain, cough, and fever. She denies leg pain or swelling and recent travel, immobilization, trauma, or surgery. She has no anterior abdominal pain, no dysuria or hematuria and no personal or family history of gallstones, kidney stones, or blood clots. She’s never had this pain before, has no significant past medical history and her only medication is birth control pills. On exam, her vital signs are within normal range, she has normal cardiac and pulmonary exams, no costovertebral angle tenderness, no chest wall or abdominal tenderness and no leg swelling.
Do you need to do any studies to evaluate this patient for a pulmonary embolism?
Pulmonary Embolism Rule-Out Criteria (PERC)
- Age ≥ 50
- Heart rate ≥ 100
- O2 sat on room air < 95%
- Prior history of venous thromboembolism
- Trauma or surgery within 4 weeks
- Hemoptysis
- Exogenous estrogen
- Unilateral leg swelling
The PERC CDR was originally derived and validated in 2004 and with a subsequent multi-study center validation in 2008. In the larger validation study, the rule was only to be applied in those patients with a pre-test probability of < 15%, therefore incorporating clinical gestalt prior to using the rule. PERC is a one-way rule, as mentioned above, which tried to identify patients who are so low-risk for pulmonary embolism (PE) as to not require any testing. It does not imply that testing should be done for patients who do not meet criteria, and it is not meant for risk stratification, as opposed to the Wells’ and Geneva scores.
Case Discussion
In order to apply the PERC CDR to the case study patient, the ED physician pre-supposes a pre-test probability of < 15%. If the ED physician has a higher pre-test probability than that, he/she should not use the PERC CDR. If the ED physician, in this case, did indeed have a pre-test probability of < 15%, the case study patient would fail the rule-out due to her use of oral contraceptives. In that case, the ED physician would need to determine if he/she would do further testing which could include a D-dimer, CT chest with contrast, ventilation/perfusion scan, or lower extremity Doppler studies to evaluate for deep vein thromboses (DVTs). The PERC CDR gives no guidance in this case.
