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Emergency Medicine & Critical CarePERC Rule

PERC Rule Calculator for Pulmonary Embolism

Check all eight PERC criteria for a low-probability adult suspected-PE assessment, with exact age, pulse, room-air oxygen, history, and examination boundaries.

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Formula and medical content are based on the references listed on this page. See sources, About, and Sources and Review Process.

Eligibility must already be established: PERC is intended only for an adult with suspected acute PE who has already been assessed as low probability (clinician gestalt below 15%). This calculator does not determine or confirm that eligibility.

Measurements

Completed years. This implementation is for adults age 18 or older; age 50 or older is a positive PERC criterion.

Current paired pulse in beats/min. A value of 100 or higher is positive.

Enter the room-air SpO₂ percentage. Below 95% is positive; exactly 95% is absent.

History and examination criteria

Assess every item explicitly. Nothing is assumed absent from an unchecked control.

Select Yes when unilateral leg swelling is present.

Select Yes when coughing blood is present.

Use the validated criterion wording; minor trauma without hospitalization is not silently counted.

Select Yes for documented previous PE or DVT (prior venous thromboembolism).

Select Yes when the validated exogenous-estrogen criterion is present.

About

This PERC Rule calculator checks all eight Pulmonary Embolism Rule-Out Criteria for a selected adult with suspected acute pulmonary embolism who has already been assessed as low probability (clinician gestalt below 15%). It does not calculate that pretest probability or decide whether PERC is eligible. [2, 7, 8]

A PERC-negative pattern means all eight criteria are absent. That pattern is conditionally meaningful only in the intended low-probability population; it is not an unconditional PE exclusion, diagnosis, individual probability, or treatment decision. [2, 3, 4]

Formula

Positive criteria count = number of the eight PERC criteria that are present. [1, 2]
PERC-negative pattern = all eight criteria absent; PERC-positive = one or more criteria present.

Interpretation

PERC result patterns and limits
PatternArithmetic meaningRequired interpretation boundary
PERC-negative pattern0 of 8 criteria presentConditionally useful only after an eligible adult suspected-PE assessment has already established low probability below 15%; not unconditional exclusion.
PERC-positiveAt least 1 criterion presentPERC cannot rule out PE. This is not a PE diagnosis, severity grade, or automatic order for D-dimer or imaging.

The count is transparency for the eight-item audit, not a graded score: 2 is not “more positive” in a validated severity sense than 1. Current diagnostic pathways keep pretest probability, PERC, D-dimer, YEARS, and imaging as distinct steps. [7, 8]

How to use the eight PERC criteria

Eligibility comes before the PERC Rule

PERC was prospectively evaluated after an emergency clinician judged the adult patient’s pretest probability to be below 15%. This page deliberately has no checkbox claiming that probability has been verified: the calculator cannot reconstruct a clinical assessment, and an entered Wells score is not inferred here. [2, 3]

Exact threshold boundaries

The positive criteria are age 50 years or older, pulse 100 beats/min or higher, room-air oxygen saturation below 95%, unilateral leg swelling, hemoptysis, qualifying surgery or trauma requiring hospitalization within the previous 4 weeks, previous PE or DVT, and exogenous estrogen use. Exactly 95% room-air saturation is PERC-negative for that item. [2]

Evidence and setting

In the 2008 prospective multicenter validation, 1,666 low-suspicion patients were PERC-negative and 16 met the study’s composite false-negative outcome (1.0%, 95% CI 0.6%–1.6%). That is a cohort result, not an individual patient probability. The PROPER trial later evaluated a PERC-based strategy in very-low-risk emergency-department patients. [2, 3]

Performance and acceptability depend on setting and baseline prevalence. The 2019 ESC guideline cautioned that low prevalence in validation studies limits generalizability, and an individual-patient-data meta-analysis found performance differed across healthcare settings. [5, 6]

Wells, D-dimer, YEARS, and PERC are different tasks

Wells estimates pretest probability from a separate weighted model. PERC checks eight rule-out criteria only after low probability is already established. D-dimer is a laboratory result, and YEARS is a separate diagnostic algorithm. This page neither combines those models nor chooses the next test. [7, 8]

Important limits

This adult implementation is not a pregnancy adaptation and should not be used to delay urgent evaluation in an unstable patient or to override a higher-probability assessment. Hospitalized or referred populations, recurrent events, anticoagulation, and other special settings may require different evidence and pathways. The result does not order testing, select imaging, prescribe treatment, or diagnose PE. [5, 6, 7, 8]

References

  1. Kline JA, et al. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost. 2004;2(8):1247–1255. PMID 15304025. DOI 10.1111/j.1538-7836.2004.00790.x.
  2. Kline JA, et al. Prospective multicenter evaluation of the pulmonary embolism rule-out criteria. J Thromb Haemost. 2008;6(5):772–780. PMID 18318689. DOI 10.1111/j.1538-7836.2008.02944.x.
  3. Freund Y, et al. Effect of the Pulmonary Embolism Rule-Out Criteria on Subsequent Thromboembolic Events Among Low-Risk Emergency Department Patients: The PROPER Randomized Clinical Trial. JAMA. 2018;319(6):559–566. PMID 29450523. DOI 10.1001/jama.2017.21904.
  4. Wolf SJ, et al. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients With Suspected Acute Venous Thromboembolic Disease. Ann Emerg Med. 2018;71(5):e59–e109. PMID 29681319. DOI 10.1016/j.annemergmed.2018.03.006.
  5. Konstantinides SV, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism. Eur Heart J. 2020;41(4):543–603. PMID 31504429. DOI 10.1093/eurheartj/ehz405.
  6. Geersing GJ, 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. PMID 35077453. DOI 10.1371/journal.pmed.1003905.
  7. 2026 AHA/ACC/ACCP/ACEP/CHEST/SCAI/SHM/SIR/SVM/SVN Guideline for the Evaluation and Management of Acute Pulmonary Embolism in Adults. Circulation. 2026;153(12):e977–e1051. PMID 41712677. DOI 10.1161/CIR.0000000000001415.
  8. Creager MA, et al. Correction to: 2026 AHA/ACC/ACCP/ACEP/CHEST/SCAI/SHM/SIR/SVM/SVN Guideline for the Evaluation and Management of Acute Pulmonary Embolism in Adults. Circulation. 2026;154(2):e24. PMID 42441758. DOI 10.1161/CIR.0000000000001462.

FAQ

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Disclaimer

Educational and informational reference only. Not intended to replace professional medical advice, diagnosis, treatment, or independent verification.