CO-55 — Experimental / investigational
Claim-adjustment reason code 55 · typically reported as CO-55 or PR-55
What it means
The payer classifies the item or its use as experimental or not yet proven for the billed indication.
Why DME claims hit it
- Newer-technology DME (or new indications) billed before the payer adopts coverage
- Miscoded item mapping to a non-covered technology code
How to fix it
- Check whether a specific covered HCPCS exists for the item
- Gather peer-reviewed evidence + physician letter if pursuing coverage
Appeal posture
Appealable but uphill: you’re arguing the science. Consider ABN/private-pay flows for known-investigational items.
Related denial codes
CO-50 — Not deemed medically necessaryCO-204 — Not covered under the patient’s current benefit planCO-96 — Non-covered charge
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