💊 PEN-FAST Penicillin Allergy Decision Rule
UseWhen to use: remote or unclear penicillin allergy labels when stewardship/delabeling is considered.
StrataScore <3 → published low risk (<5%); consider supervised DOC per protocol. ≥3 → allergy evaluation preferred.
LimitsWhen not to use: recent anaphylaxis or SCAR — do not direct-challenge. · Pitfall: confusing non-allergic intolerance with IgE/SCAR history. · Follow institutional allergy pathways.
SourceTrubiano JA, et al. JAMA Intern Med 2020 (PEN-FAST)
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
Methodology · worked example, guidelines & full notes
Cutoff <3 low risk.
When to use
When to use: remote or unclear penicillin allergy labels when stewardship/delabeling is considered.
How it works
≤5 years since reaction or unknown (2) + anaphylaxis/angioedema or SCAR (2) + treatment required or unknown (1). 0–5.
Key points
- Cutoff <3 low risk.
- Adapted interview tool.
- Next: SULF-FAST / allergy referral.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Five years or less since reaction (or unknown timing) | No — >5 y ago (0) |
|---|---|
| Anaphylaxis / angioedema OR severe cutaneous adverse reaction (SCAR) | No (0) |
| Treatment required for the reaction (or unknown) | No (0) |
→PEN-FAST0/5
- Band：Low risk of true allergy (<5% in validation) — DOC pathways often considered
- Cutoff：<3 low risk
| Five years or less since reaction (or unknown timing) | Yes / unknown (2) |
|---|---|
| Anaphylaxis / angioedema OR severe cutaneous adverse reaction (SCAR) | Yes (2) |
| Treatment required for the reaction (or unknown) | Yes / unknown (1) |
→PEN-FAST5/5
- Band：Elevated risk (≥3) — allergy evaluation / testing preferred before rechallenge
- Cutoff：<3 low risk
Verification & sources · governance
FAQ
Frequently asked questions
- Does PEN-FAST Penicillin Allergy Decision Rule upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is PEN-FAST Penicillin Allergy Decision Rule calculated in practice? Can you show a worked example?
- Inputs: Five years or less since reaction (or unknown timing) No — >5 y ago (0), Anaphylaxis / angioedema OR severe cutaneous adverse reaction (SCAR) No (0), Treatment required for the reaction (or unknown) No (0) → Result: PEN-FAST 0 /5（Band: Low risk of true allergy (<5% in validation) — DOC pathways often considered, Cutoff: <3 low risk） Inputs: Five years or less since reaction (or unknown timing) Yes / unknown (2), Anaphylaxis / angioedema OR severe cutaneous adverse reaction (SCAR) Yes (2), Treatment required for the reaction (or unknown) Yes / unknown (1) → Result: PEN-FAST 5 /5（Band: Elevated risk (≥3) — allergy evaluation / testing preferred before rechallenge, Cutoff: <3 low risk）