PERC Rule Calculator

PERC Rule Calculator for Hematology. In the intended low-risk setting, a negative rule can support avoiding further PE testing. A positive rule means PERC cannot exclude PE; it does not diagnose PE or mandate immediate CT.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

PERC checks eight adverse findings only after a clinician has judged PE probability very low. A negative rule requires all eight to be absent. The intended estrogen criterion should not be broadened automatically to every contraceptive preparation.

When to use this calculator

Use within an appropriate very-low-risk adult emergency diagnostic pathway. A generic low Wells category is not automatically the same as the clinician-selected very-low-risk population in PERC studies.

Inputs used

  • Age
  • Heart rate
  • Oxygen saturation
  • Hemoptysis
  • Estrogen use
  • Prior VTE
  • Recent surgery or trauma
  • Unilateral leg swelling

Clinical interpretation

In the intended low-risk setting, a negative rule can support avoiding further PE testing. A positive rule means PERC cannot exclude PE; it does not diagnose PE or mandate immediate CT.

Worked example

Age 42, pulse 88, oxygen saturation 97%, and absence of all remaining adverse findings produce PERC 0. At exactly age 50 or pulse 100, the corresponding adverse item is positive; saturation exactly 95% does not meet the below-95 criterion.

Limitations and safety notes

All items must be assessed, including the specified recent trauma/surgery context. Do not use missing findings as negative. The rule is not a general screening test or a substitute for pregnancy-specific or unstable-patient pathways.

Frequently asked questions

Does one positive PERC finding prove PE?

No. It only prevents exclusion by this rule; subsequent testing depends on the full pretest-probability pathway.

References

  • Kline et al. Prospective multicenter PERC evaluation. 2008: https://pubmed.ncbi.nlm.nih.gov/18318689/
  • PROPER randomized clinical trial. 2018: https://pubmed.ncbi.nlm.nih.gov/29450523/

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 7, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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