For healthcare professionals
PERC rule calculator
The Pulmonary Embolism Rule-out Criteria (PERC) are 8 yes or no criteria clinicians use in the emergency department when they already judge the chance of pulmonary embolism (PE) to be low. If all 8 are met, the rule suggests no further testing for PE, not even a D-dimer. This calculator is written for clinicians and is not a diagnosis.
Rule-out criteria
For adults in whom PE is being considered. Nothing you enter leaves this page.
What you will see
Whether the rule is negative (all 8 criteria met) or positive, and which criteria are not met.
Educational only, not medical advice. Not a diagnosis. PE is confirmed or excluded by clinical assessment and testing, not by this rule alone.
Source
Kline JA et al., J Thromb Haemost 2004, the original PERC paper. The 8 criteria are taken from two open-access (CC BY) papers that print them: Freund Y et al., Trials 2015 (PROPER trial protocol) and Geersing GJ et al., Diagn Progn Res 2018, Table 1. The tests check each cut point and each history item.
Validated in
Emergency department patients with suspected PE and a low clinical probability (under 15%) by the physician's gestalt; Kline and colleagues developed the rule in 2004 and found PE in 1.4% of PERC-negative patients (Freund 2015). A 2022 individual patient data meta-analysis evaluated PERC in self-referral emergency care and in patients referred to secondary care (Geersing 2022).
Limits
Use only when the gestalt probability is already low. In the 2022 meta-analysis PERC excluded PE in 21% of suspected patients in self-referral emergency care with a failure rate of 1.12%, but the failure rate rose to 6.01% in patients referred to secondary care. European studies in high-prevalence settings reported more missed PE. The papers used here print the item as 'recent trauma or surgery' without a time window. Adults only.
The 8 PERC criteria
A patient is PERC negative only if every criterion is met. In the 2004 study the rule was applied to patients with a low clinical probability of PE, under 15% by clinical gestalt (Freund 2015).
| Criterion | Met when |
|---|---|
| Age | under 50 years |
| Pulse | under 100 beats per minute |
| Oxygen saturation (SpO2) | over 94% |
| Unilateral leg swelling | absent |
| Hemoptysis | absent |
| Recent trauma or surgery | absent |
| Prior PE or DVT | absent |
| Exogenous estrogen use | absent |
Source: the PERC rule of Kline et al., 2004 (Kline 2004), as printed in Freund et al., 2015 (Freund 2015) and Geersing et al., 2018, Table 1 (Geersing 2018).
How the rule is used
The rule was designed to cut D-dimer testing and imaging in patients whose pretest probability is so low that testing may do more harm than good (Freund 2015). In the PERC-based strategy of the PROPER trial protocol, patients with all criteria met had no further testing for PE; patients with at least one criterion not met had a sensitive D-dimer test, followed by CT pulmonary angiography if it was positive (Freund 2015). Meta-analyses cited in that protocol reported PE in under 1% of PERC-negative patients after follow-up (Freund 2015).
Performance depends on the setting. In a 2022 individual patient data meta-analysis, PERC (combined with low gestalt or a Wells score of 4 or less) excluded PE in 21% of patients in self-referral emergency care at a failure rate of 1.12%, while in patients referred to secondary care the failure rate was 6.01% (Geersing 2022). Studies in Europe, where more emergency patients with suspected PE have it, reported more missed cases (Freund 2015).
Related tools
For patients who are not low risk by gestalt, or who fail any PERC criterion, the Wells score for PE sets the pretest probability before D-dimer or imaging. Once pulmonary embolism is confirmed, the PESI score calculator gives the 30-day mortality class. For a swollen or painful leg, see the Wells score for DVT. For other clinician scores on this site, see the HEART score calculator for chest pain and the qSOFA score calculator for suspected infection.
Sources
- Freund Y, Rousseau A, Guyot-Rousseau F, et al. PERC rule to exclude the diagnosis of pulmonary embolism in emergency low-risk patients: study protocol for the PROPER randomized controlled study. Trials. 2015;16:537. doi:10.1186/s13063-015-1049-7. Open access (CC BY 4.0). Background, "The PERC rule" (the 8 criteria of Kline et al. 2004, the low gestalt probability under 15 %, PE prevalence in PERC-negative patients) and Discussion. pmc.ncbi.nlm.nih.gov/articles/PMC4660778/
- Geersing GJ, Kraaijpoel N, Buller HR, et al. Ruling out pulmonary embolism across different subgroups of patients and healthcare settings: protocol for a systematic review and individual patient data meta-analysis (IPDMA). Diagn Progn Res. 2018;2:10. doi:10.1186/s41512-018-0032-7. Open access (CC BY 4.0). Table 1 (PERC items). pmc.ncbi.nlm.nih.gov/articles/PMC6460525/
- Geersing GJ, Takada T, Klok FA, et al. Ruling out pulmonary embolism across different healthcare settings: a systematic review and individual patient data meta-analysis. PLoS Med. 2022;19(1):e1003905. doi:10.1371/journal.pmed.1003905. Open access (CC BY 4.0). Abstract and Methods (PERC with low gestalt or Wells 4 or less, by care setting). pmc.ncbi.nlm.nih.gov/articles/PMC8824365/
- Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247-1255. doi:10.1111/j.1538-7836.2004.00790.x. Original PERC paper (not open access; criteria taken from the open-access papers above). doi.org/10.1111/j.1538-7836.2004.00790.x
Written and maintained by the uncovermyrisk.com editorial team. We do not have a medical reviewer; every claim links to its primary source above. Last reviewed: 2026-11-01. Spotted an error? See About.