EviCore, Carelon, and AIM: Why Prior Auth Denials Get Routed to the Wrong Reviewer

The Vendor Delegation Layer Most Billing Teams Don't Account For

Many payers delegate prior authorization and utilization review for specific service categories — advanced imaging, certain specialty drugs, musculoskeletal procedures, radiation therapy — to third-party vendors like EviCore, Carelon (formerly AIM Specialty Health), or similar organizations, rather than reviewing those requests internally. A denial that appears to come from the payer may actually have been decided by one of these vendors under delegated authority, which changes where and how it needs to be appealed.

Why This Causes Misrouted Appeals

Billing staff who send an appeal to the payer directly, when the original review and denial was made by a delegated vendor, often see that appeal sit unresolved or bounce back, because the payer doesn't have the clinical review file — the vendor does. Identifying whether a given denial was vendor-delegated, and routing the appeal to the correct entity, is a step that's easy to skip under deadline pressure but that determines whether the appeal gets reviewed at all.

How to Identify a Vendor-Delegated Denial

The denial notice or EOB often references the vendor by name, or the original prior authorization request was submitted through the vendor's own portal rather than the payer's — both are reliable signals. Building a reference of which service categories are vendor-delegated for each of your major payers (this varies by payer and can change) helps staff catch this before misrouting the appeal.

What This Means for Specialty-Heavy Practices

Specialties that rely heavily on advanced imaging, injections, or specialty drug administration — pain management, oncology, radiology-adjacent specialties — are disproportionately exposed to vendor-delegated review, and benefit most from building this identification step explicitly into their denial intake process rather than treating every denial as payer-direct by default.