Researchers examined the use of a pulmonary embolism rule-out criteria (PERC) rule and found it to be associated with a low failure rate in a recent study, suggesting use of this approach may safely detect patients who have an unlikely probability of having a pulmonary embolism (PE). The study findings were reported in the journal Academic Emergency Medicine.

The PERC rule includes 8 criteria for ruling out a PE diagnosis in certain patients who are negative for the PERC criteria (PERC-N). The researchers conducting aimed to evaluate the safety of following this rule.

This retrospective study involved patients who had had venous thromboembolism and were included in the international, prospective Registro Informatizado de la Enfermedad TromboEmbolica venosa (RIETE) registry. The study’s primary outcome was the failure rate of the PERC rule. This was assessed based on the proportion of patients who had experienced PE but who had been considered PERC negative (PERC-N) by the standards of the PERC rule.

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Secondary outcomes involved identifying characteristics of PERC-N patients in the analysis, as well as to characterize the localization of PE experienced by these patients, and to identify if the proportion of patients considered PERC-N was going down over time.

There were 48,903 patients who had acute PE who were identified in the registry and included in the analysis. Of these patients, 346 had been considered PERC-N. This translated into a failure rate of 0.7% (95% CI, 0.6%-0.8%) for the PERC rule in this population.

Patients with acute PE who were considered PERC-N more frequently presented with chest pain and a lower respiratory rate. However, dyspnea, syncope, and hypotension were less commonly seen in these patients than in PERC-positive (PERC-P) patients. Additionally, PE in PERC-N patients occurred more often in subsegmental or segmental arteries.

Direct oral anticoagulants were more frequently given to PERC-N patients PERC-N (9.3%) than to PERC-P patients (2.8%), and mechanical or pharmacologic thrombolysis strategies were less frequently used in PERC-N patients. During anticoagulation, PERC-N patients showed lower rates of developing recurrent deep vein thrombosis, major bleeding or death than were seen among PERC-P patients.

The relative proportion of PERC-N patients in the registry, compared with PERC-P patients, did not appear to change between 2001 and 2015. However, after 2015 there was a significant increase in the proportion considered PERC-N (P <.05).

“A low failure rate of the PERC rule was observed in the RIETE registry, thus supporting its use to safely identify patients with an unlikely probability of PE according to a Wells’ score of 4 points or less,” the researchers concluded in their report. However, they noted the observational nature of the study and a certain proportion of missing data as possible contributors to uncertainty with identifying the true failure rate of the PERC rule.


Truong P, Mazzolai L, Font C, et al; the RIETE Investigators. Safety of the pulmonary embolism rule-out criteria rule: findings from the Registro Informatizado de la Enfermedad TromboEmbolica venosa (RIETE) Registry. Acad Emerg Med. Accepted manuscript. Published online April 24, 2023. doi:10.1111/acem.14744