PEN-FAST Penicillin Allergy Rule
PEN-FAST penicillin-allergy rule (Trubiano 2020): reaction within five years (+2), anaphylaxis/angioedema or severe cutaneous reaction (+2), treatment required (+1); total 0-5 and < 3 is low risk.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Reaction within the last five years
- Yes
- Anaphylaxis/angioedema OR severe cutaneous reaction
- Yes
Result: PEN-FAST score 4 of 5 — not low risk (>= 3), refer for allergist evaluation.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- < 3
- Low risk (NPV > 95%); consider a direct oral challenge.
- >= 3
- Not low risk; refer for allergist evaluation (Five years, Anaphylaxis/SCAR, Treatment required). A decision rule, not a diagnosis.
What you enter
- Reaction within the last five years
- Anaphylaxis/angioedema OR severe cutaneous reaction
- Treatment required for the reaction
How this is calculated
Trubiano JA, Vogrin S, Chua KYL, et al. Development and validation of a penicillin allergy clinical decision rule (PEN-FAST). JAMA Intern Med. 2020;180(5):745-752. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.