CO-55 means the payer classifies the procedure, treatment or drug as experimental or investigational, so the plan does not cover it. The question is the payer's medical policy, not the claim form. Start with the policy in effect on the date of service, then decide whether the patient fits an exception or the classification itself can be challenged.
CO-55: "Procedure/treatment/drug is deemed experimental/investigational by the payer."
Find the payer's written policy for the CPT or HCPCS code, device or drug, and confirm which version applied on the date of service. Commercial payers publish these in policy libraries, such as Aetna's Clinical Policy Bulletins and UnitedHealthcare's medical policies, and Medicare's are in the CMS Medicare Coverage Database.
Read three things in the policy: whether the service is listed as experimental or investigational, for which indications, and whether the policy names exceptions or criteria under which it is covered. The answer decides whether the next step is a corrected claim, an exception request or an appeal of the classification.
Commercial plans define "experimental or investigational" in the member's plan documents, and their medical policies apply that definition to specific services. Those definitions commonly look at regulatory approval for the use in question, published evidence that the service improves outcomes, and acceptance in professional guidelines.
Medicare covers items and services that are "reasonable and necessary for the diagnosis or treatment of an illness or injury," in CMS's words, and applies that test through national and local coverage determinations. A service that lacks evidence for an indication fails that test even without the word "experimental."
CPT Category III codes are, in the AMA's description, "a temporary set of codes for emerging technologies, services and procedures." Having a code does not mean a payer covers the service, and many payer policies treat Category III services as investigational.
Quote the plan's definition of experimental or investigational and the policy section the payer applied. The appeal argues against their exact wording.
For a device, include the FDA approval or clearance and the indication it covers. Drugs need the labeled indication and, for an off-label use, the compendia listings or guidelines that support it.
Attach peer-reviewed studies and professional society guidelines that support the service for this indication. Recent publications matter most, because a policy may predate newer evidence.
The treating physician writes a letter explaining why standard options failed or were contraindicated. An exception is argued for one patient, so the letter has to be about this patient.
Ask whether the payer reviews exceptions case by case. For most non-grandfathered commercial plans, federal rules at 45 CFR 147.136 give the member a right to external review of a denial based on a determination that treatment is experimental or investigational.
These categories show up most often in payer experimental and investigational policies. The list reflects policy content, not a measured denial frequency.
X12 also has CARC 56, "Procedure/treatment has not been deemed 'proven to be effective' by the payer," which some payers use for similar decisions. The appeal approach is the same.
Check the policy at scheduling. Flag Category III codes, new devices and off-label drug orders for a policy check before the service is booked.
Ask for a pre-service determination. Many commercial payers will review coverage before the service on request. A written answer before treatment is easier to work with than a denial after it.
Get the patient's informed financial consent. For Medicare, an Advance Beneficiary Notice of Noncoverage (Form CMS-R-131) signed before the service lets the practice bill the patient if Medicare denies it. Commercial plans set their own waiver rules by contract and state law.
Track policy updates. Payers revise experimental and investigational policies as evidence changes, and a service denied last year may be covered now. For groups with several sites, we track these policy changes centrally as part of our billing for group practices.
We check payer policy before the service and build the exception or appeal packet when a denial comes back.
Learn About Our Denial Management →CARC 55 reads "Procedure/treatment/drug is deemed experimental/investigational by the payer." The payer's medical policy does not cover the service for this use. The CO group code makes the amount the provider's responsibility unless the denial is overturned or a valid patient waiver applies.
Commercial plans apply the definition in the member's plan documents through their medical policies. Those definitions commonly weigh FDA status for the use, published evidence of benefit and professional guidelines. Medicare asks whether the service is reasonable and necessary under its coverage determinations.
Include the plan's definition and the policy applied, the FDA status for the device or drug, peer-reviewed literature and guidelines, and a letter on why this patient needed the service. Ask whether the payer grants exceptions case by case. Most non-grandfathered commercial plans also allow external review of experimental or investigational denials.
No. A missing authorization is CO-197, while CO-55 is a coverage decision about the service itself. An authorization request can surface the experimental classification early, which is one reason to request one for new procedures.
