# AI orders CT with IV contrast for a patient with documented severe contrast allergy, no premedication ordered

- **ID:** `medical/contrast-allergy-history-missed`
- **Domain:** medical
- **Category:** data_error
- **Error Code:** `CONTRAST-ALLERGY-002`
- **Verification:** ai_generated
- **Fix Rate:** 85%

## Root Cause

Skipping premedication (e.g., prednisone, diphenhydramine) for patients with prior anaphylactoid reaction to iodinated contrast can trigger life-threatening anaphylaxis; electronic health record allergy alerts are often overlooked.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| iohexol 350mgI/mL | active | — | — |
| ACR manual on contrast media v2023 | active | — | — |
| EHR allergy module v5.2 | active | — | — |

## Workarounds

1. **Order premedication: prednisone 50mg PO at 13h, 7h, 1h before scan + diphenhydramine 50mg IV 1h before; use `python -c "print('Premed: pred 50mg PO at t-13, t-7, t-1; benadryl 50mg IV at t-1')"`** (90% success)
   ```
   Order premedication: prednisone 50mg PO at 13h, 7h, 1h before scan + diphenhydramine 50mg IV 1h before; use `python -c "print('Premed: pred 50mg PO at t-13, t-7, t-1; benadryl 50mg IV at t-1')"`
   ```
2. **If urgent scan needed, use emergency premedication (methylprednisolone 40mg IV + diphenhydramine 50mg IV) 1h prior** (85% success)
   ```
   If urgent scan needed, use emergency premedication (methylprednisolone 40mg IV + diphenhydramine 50mg IV) 1h prior
   ```
3. **Consider alternative imaging without contrast (e.g., non-contrast CT, MRI with gadolinium if no contraindication)** (80% success)
   ```
   Consider alternative imaging without contrast (e.g., non-contrast CT, MRI with gadolinium if no contraindication)
   ```

## Dead Ends

- **** — Low-osmolar reduces but does not eliminate risk in patients with prior severe reaction; premedication still indicated (80% fail)
- **** — Anaphylaxis can occur within minutes regardless of infusion rate; reactive monitoring is insufficient (85% fail)
- **** — Non-ionic contrast still carries risk; premedication protocol applies to all iodinated contrast agents (75% fail)