Cigna's PxDx system let doctors reject 300,000 claims in two months without reading them
A ProPublica investigation found Cigna used a system called PxDx to automatically flag mismatched claims for bulk denial, letting its medical directors reject about 300,000 claims over two months, an average of 1.2 seconds each, without opening patient files. Lawsuits and a congressional inquiry followed.
Cigna doctors spent an average of 1.2 seconds on each of about 300,000 claims they denied without reading the files.
Key facts
- What
- A ProPublica investigation found Cigna used a system called PxDx to automatically flag mismatched claims for bulk denial, letting its medical directors reject about 300,000 claims over two months, an average of 1.2 seconds each, without opening patient files.
- Incident date
- Mar 25, 2023
- Who
- Cigna
- Failure mode
- Policy Violation
- AI surface
- Agentic Workflow
- Severity
- Catastrophic
What happened
In 2023 ProPublica and The Capitol Forum reported that Cigna's PxDx system batched claims that did not match an approved list and routed them for bulk denial, with doctors rejecting about 300,000 claims in two months at an average of 1.2 seconds each, without reviewing patient files. The reporting triggered class actions and a congressional inquiry.
What broke inside the model
- 01 · TriggerA prompt pushes against a deployment boundary.
- 02 · Model stepThe model produces the disallowed output.
- 03 · Control gapNo enforcement blocks it at generation time.
- 04 · FailureThe output crosses the policy line.
- 05 · ConsequenceA limit the business set is breached in public.
The output crosses a policy boundary the deployment had defined.
The system produced an output or action that broke a stated company policy or a regulation that applied to the deployment. The model optimized for a plausible response, not for the constraint, and no enforcement layer checked the output against the policy before it took effect.
What it cost
~300,000 claims denied in two months; class actions and congressional scrutiny
Sources
Cite this entry
https://failureindex.ai/failures/cigna-pxdx-system-let-doctors-rejectAI Failure Index. "Cigna's PxDx system let doctors reject 300,000 claims in two months without reading them" (FI-0038). Realm Labs. https://failureindex.ai/failures/cigna-pxdx-system-let-doctors-reject (indexed Jun 3, 2026).Data fields CC-BY 4.0, prose citation permitted. Incident ID FI-0038. Full dataset at /data.
Note from Realm Labs, the Index steward
How Realm would have caught this
- Prism
- OmniGuard
Realm compares what the model is about to output or do against the policy that governs the deployment, in real time, and can deny or redact the action before it takes effect, which is the gap an after-the-fact review never closes in time.