Quick Explanation
Denial code CO 171 indicates that payment has been adjusted or denied because the prescribed item, medication, or clinical protocol is not covered under the payer's current formulary. In the context of behavioral health and ABA therapy, this typically arises when associated prescribed supplies, pharmacological interventions, or specialized tools are excluded from the plan's approved formulary list. Resolving this denial requires verifying formulary alignment, securing administrative overrides, or correcting benefit classification mismatches.
Common Causes for CO 171
Denials with code CO 171 typically happen for the following specific reasons:
- The prescribed medication or specialized clinical tool accompanying the ABA therapy plan is classified as non-formulary or excluded under the patient's behavioral benefit plan.
- Failure to submit or obtain an approved formulary exception or prior authorization for a restricted or non-preferred prescribed item prior to billing.
- Incorrect billing practices where ABA therapeutic services (such as CPT 97151-97158) are mistakenly mapped or billed under pharmacy/formulary benefit structures rather than medical benefits.
- The payer's benefit design excludes specific developmental pediatric prescriptions or behavioral medical devices from their covered medical or pharmacy formulary.
How to Prevent CO 171 Denials
To avoid receiving this denial in the future, implement these specific checks:
- Conduct proactive eligibility and benefits verification to determine the patient's specific formulary requirements and exclusions before initiating treatment.
- Utilize the payer's online portal to check the Preferred Drug List (PDL) or covered medical supplies formulary for behavioral health services.
- Submit a comprehensive formulary exception request backed by clinical documentation of medical necessity prior to prescribing non-preferred items.
- Ensure strict separation of medical billing codes (such as CPT codes 97153 or 97155) from pharmacy or prescription benefit claims to prevent administrative mapping errors.
Appeal Letter Template for CO 171
If you believe this claim was denied incorrectly, you can use the following template to submit an appeal.
[Your Practice Header]
[Date]
[Payer Name]
[Appeals Department Address]
RE: Appeal for Claim [Claim Number]
Patient: [Patient Name]
ID: [Patient ID]
Date of Service: [Date]
Denial Code: CO 171 - ABA Therapy denial code
Dear Appeals Department,
I am writing to appeal the denial of the above-referenced claim, which was denied with code CO 171: "ABA Therapy denial code".
We are writing to formally appeal the denial under code CO 171 for the prescribed treatment associated with the patient's Applied Behavior Analysis (ABA) therapy. The prescribed protocol is clinically necessary and integral to the patient's individualized behavioral intervention plan for Autism Spectrum Disorder (ASD). In accordance with the American Medical Association (AMA) guidelines and State Autism Insurance Mandates, comprehensive behavioral treatment must be supported by necessary clinical resources. Alternative formulary options are clinically inappropriate and would severely disrupt the continuity of the patient's established treatment plan. We have enclosed the patient's clinical evaluations, DSM-5 diagnostic criteria, and a formal letter of medical necessity from the prescribing clinician. We request an immediate formulary exception and administrative override to approve coverage for this medically necessary service.
Attached please find:
1. A copy of the original claim.
2. The relevant medical records supporting the service.
3. [Any other supporting documents].
We respectfully request that you reprocess this claim for payment.
Sincerely,
[Your Name]
[Title]
[Practice Name]
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