CPT 78816 PET/CT Scan Denied by Medicare (Traditional)? Appeal Guide & Letter Template

Imaging · 7 min read ·

Why Medicare (Traditional) Denies CPT 78816 (PET/CT Scan)

Medicare (Traditional) denies CPT 78816 claims for several documented reasons. Understanding the specific denial reason on your Explanation of Benefits (EOB) is the critical first step before writing your appeal.

Common Denial Reasons for CPT 78816

Medical Necessity Not Established (CO-50, CO-236)
Medicare determines that pet/ct scan does not meet their internal clinical criteria for your diagnosis. For imaging procedures like pet/ct scan, Medicare typically requires documentation of failed conservative treatment (4-6 weeks minimum), specific clinical findings on physical exam, and a clear diagnostic question that cannot be answered by less expensive imaging modalities. If an X-ray or ultrasound could reasonably answer the clinical question, the advanced imaging may be denied.

Prior Authorization Not Obtained (CO-15, CO-197)
Most Medicare plans require prior authorization for CPT 78816 (PET/CT Scan). If the procedure was performed without prior auth, the claim will be denied regardless of medical necessity. However, you may be able to obtain retroactive authorization, especially if the service was urgent or medically necessary. Check your specific plan's policies on retro-auth at medicare.gov.

Conservative Treatment Not Exhausted (CO-50)
Medicare may require 4-6 weeks of conservative management (physical therapy, activity modification, NSAIDs) before approving advanced imaging. If the patient has red flag symptoms (neurological deficits, suspected fracture, cancer history), conservative treatment requirements may be waived — but this must be clearly documented.

Documentation Insufficient (CO-16, CO-252)
Clinical documentation submitted does not support the medical necessity for pet/ct scan. Medicare requires specific elements that demonstrate the procedure meets their coverage criteria.

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Medicare (Traditional) Denial Rate Statistics

Understanding how often Medicare denies claims — and how often those denials are overturned — can help you decide whether to appeal.

| Metric | Data |
|--------|------|
| Medicare Overall Denial Rate | 7.38% improper payment rate (FFS) |
| Industry Average Denial Rate | 19% of in-network claims denied across HealthCare.gov plans (2023) |
| % of Denials Appealed | Less than 1% of denied claims are appealed by consumers |
| % of Appeals Overturned | 44% of appealed denials are overturned at internal appeal |
| Medicare Advantage Overturn Rate | 57% of MA denials overturned on appeal |
| Cost to Rework a Denied Claim | $25 to $181 per reworked claim |

Sources: KFF analysis of CMS QHP Transparency Data (2023), published Jan 2025; Health Affairs, "Medicare Advantage Denies 17 Percent of Initial Claims" (2025)

The key takeaway: The vast majority of denied claims are never appealed. But when providers do appeal, nearly half succeed. For a pet/ct scan with CPT 78816, the reimbursement at stake typically makes the appeal worth pursuing.

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Step-by-Step: How to Appeal a CPT 78816 Denial from Medicare (Traditional)

Step 1: Identify the Exact Denial Reason

Read your EOB or remittance advice carefully. Look for:


If the denial letter references a specific Medicare medical policy number, request a copy of that policy. You are legally entitled to this under ERISA §503 (employer plans) or ACA §2719 (individual/marketplace plans).

Step 2: Review Medicare (Traditional)'s Coverage Criteria

Medicare coverage criteria are published at cms.gov/medicare-coverage-database. Search by CPT 78816 to find applicable NCDs (National Coverage Determinations) and LCDs (Local Coverage Determinations). LCDs vary by Medicare Administrative Contractor (MAC), so identify your regional MAC first.

Compare the criteria point-by-point against your clinical documentation. Identify exactly which criterion Medicare claims was not met.

Step 3: Gather Supporting Documentation

For a CPT 78816 appeal, you will need:


Step 4: Write Your Appeal Letter

Your appeal letter should include:


Pro tips for CPT 78816 appeals to Medicare (Traditional):

Step 5: Submit the Appeal Within the Deadline

| Appeal Detail | Medicare (Traditional) |
|--------------|---------------|
| Appeal Window | 120 days for redetermination (Level 1); 180 days for QIC reconsideration (Level 2) |
| Submit Appeals To | Varies by Medicare Administrative Contractor (MAC) |
| Appeals Fax | Varies by MAC |
| Provider Portal | medicare.gov |

Important: Always send appeals via certified mail or fax with confirmation. Keep copies of everything.

Step 6: Request a Peer-to-Peer Review

For CPT 78816 denials based on medical necessity, request a peer-to-peer review between the ordering/performing physician and Medicare's medical director. This is often the most effective intervention — many denials are overturned during peer-to-peer without a formal written appeal.

Contact Medicare at Varies by MAC — check cms.gov/Medicare/Medicare-Contracting/Medicare-Administrative-Contractors to schedule.

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Appeal Deadlines and Key Contacts for Medicare (Traditional)

| Resource | Details |
|----------|---------|
| Prior Auth Phone | Varies by MAC — check cms.gov/Medicare/Medicare-Contracting/Medicare-Administrative-Contractors |
| Appeals Mailing Address | Varies by Medicare Administrative Contractor (MAC) |
| Appeals Fax | Varies by MAC |
| Provider Portal | medicare.gov |
| Appeal Deadline | 120 days for redetermination (Level 1); 180 days for QIC reconsideration (Level 2) |

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Frequently Asked Questions

How long does it take Medicare (Traditional) to process a CPT 78816 appeal?
Medicare must respond to standard appeals within 30-60 days (varies by plan type and state). For urgent/expedited appeals involving active treatment, the response time is 72 hours under federal regulations.

Can I appeal a CPT 78816 denial if the prior authorization was not obtained?
Yes. You can request retroactive authorization for many procedures, especially if the service was medically necessary and the failure to obtain prior auth was administrative. Include documentation explaining why prior auth was not obtained and evidence of medical necessity.

What if Medicare (Traditional) denies my appeal?
You have the right to an external independent review. Under ACA Section 2719 and ERISA regulations, an independent review organization (IRO) will evaluate your appeal. External reviewers overturn a meaningful percentage of upheld internal denials. You can also escalate to your state insurance commissioner.

What denial codes are most common for CPT 78816?
The most common CARC codes for pet/ct scan denials are CO-50 (medical necessity not met), CO-15 (prior auth required), CO-16 (missing information), and CO-197 (precertification/authorization not obtained). Each requires a different appeal strategy.

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