Custom GPT: Your Prior Authorization Appeal Letter Generator

What This Builds

Instead of spending 20–40 minutes drafting each prior authorization appeal letter from scratch, you'll have a Custom GPT that takes a clinical indication and generates a complete, insurance-ready appeal letter in under 2 minutes — every time. The Custom GPT knows ACR Appropriateness Criteria language, common insurance denial reasons, and the structure that gets appeals approved.

Prerequisites

• ChatGPT Plus subscription ($20/month — required for Custom GPTs)
• Comfortable using ChatGPT for basic writing tasks (Level 3)
• Familiar with your department's most common denied procedures (you'll list these in setup)

The Concept

A Custom GPT is like a specialized version of ChatGPT that you've pre-trained for a specific purpose. Instead of explaining the context every time ("I'm writing a prior auth appeal for..."), the Custom GPT already knows: the standard letter format, ACR criteria language, common denial reasons and counter-arguments, and your department's typical procedures. You just input the clinical situation — it outputs the letter.

Think of it as building a very knowledgeable, very fast administrative assistant who only does one job: writes prior auth appeals.

Build It Step by Step

Part 1: Set Up Your Custom GPT

1. Log in to chat.openai.com with a ChatGPT Plus account
2. Click your profile icon (top right) → "My GPTs" → "+ Create a GPT"
3. You'll see a two-panel screen: left panel is the builder interface, right is a preview

What you should see: A "Configure" tab and a "Create" tab. Use Configure — it gives you more control.

1. Click "Configure" tab
2. Fill in the Name field: "Prior Auth Appeal Assistant"
3. Fill in the Description: "Generates prior authorization appeal letters for radiology imaging procedures. For use by radiologic technologists and imaging department staff."

Part 2: Write the System Instructions

This is the most important step. In the "Instructions" field, paste the following system prompt (customize the bracketed sections for your facility):

You are a prior authorization appeal letter assistant for a radiology imaging department. Your job is to generate professional, persuasive prior authorization appeal letters for insurance carriers when imaging studies are denied.

WHAT YOU DO:
When the user provides: (1) the imaging procedure, (2) the clinical indication, and (3) any previous treatments or workup, you generate a complete appeal letter that:
- Opens with a clear statement of appeal purpose
- States the clinical indication in medical necessity language
- References ACR Appropriateness Criteria (category "Usually Appropriate" or "May Be Appropriate") for the specific indication
- Describes failed conservative treatment if applicable
- Requests expedited review if clinically urgent
- Closes with contact information placeholders

WHAT YOU DO NOT DO:
- Never fabricate clinical findings or patient history
- Never include specific patient names, dates of birth, or PHI
- Always include clear [PLACEHOLDER] brackets for anything the user must fill in (patient initials, ordering provider name, date, specific clinical findings)
- If the indication is unclear, ask one clarifying question before generating

FORMAT:
- Use standard business letter format
- 200-250 words maximum
- Professional but not overly technical — insurance reviewers vary in clinical background

COMMON PROCEDURES YOU SUPPORT:
- Lumbar/cervical/thoracic spine MRI
- Knee/shoulder MRI
- Brain MRI
- CT abdomen/pelvis
- Chest CT for lung nodule follow-up
- Pelvic MRI
- Abdominal ultrasound

Click Save after pasting.

Part 3: Add Conversation Starters

Scroll down to "Conversation starters" and add these prompts so users know how to use the GPT:

• "Write an appeal for lumbar spine MRI for low back pain"
• "Appeal for knee MRI after conservative treatment failed"
• "Write an appeal for CT abdomen for unexplained weight loss"
• "Appeal for brain MRI ordered for headaches"

Click Save.

Part 4: Test and Refine

Click "Preview" (the right panel) to test your Custom GPT.

Try this test input:

What good output looks like:

• Letter is 200–250 words
• Mentions ACR Appropriateness Criteria
• Has clear [PLACEHOLDER] brackets for anything you need to fill in
• Reads professionally without being overly dense

If the output is too long, add to your instructions: "Always aim for 200 words maximum." If it's missing ACR references, add: "Always cite the relevant ACR Appropriateness Criteria category in the letter."

Part 5: Publish and Use

Click "Save" on the Configure page → Select "Only me" for access (keep this private — for your professional use only). Click "Update".

Your Custom GPT now appears in your "My GPTs" list and can be accessed any time from your ChatGPT sidebar.

Real Example: Knee MRI After PT Failure

Setup: Your Custom GPT has the system instructions from Part 2.

Input: "Appeal for left knee MRI. Patient is 45 years old, 3 months of medial knee pain, completed 8 weeks of PT with no improvement, has mechanical symptoms. Orthopedist ordered to rule out meniscal tear."

Output: A complete appeal letter with:

• Clinical indication stated as medical necessity
• Reference to ACR Appropriateness Criteria for "knee pain with suspected internal derangement"
• Conservative treatment documented (8 weeks PT, failed)
• [PATIENT INITIALS], [ORDERING PROVIDER], [DATE], [INSURANCE CLAIM NUMBER] placeholders clearly marked
• Request for expedited review since patient has mechanical symptoms

Time saved: 30 min → 2 min. You spend the remaining 28 minutes on actual patient care.

What to Do When It Breaks

• "The letter is too generic" → Add specifics to your input: exact symptoms, specific procedures tried, exact duration. The more detail you give, the better the output.
• "It's generating PHI placeholders with real-sounding data" → This shouldn't happen with the instructions above, but if it does, review your system prompt and ensure the "never fabricate clinical findings" line is present.
• "It won't generate letters for certain procedures" → Add the procedure to your "Common Procedures" list in the system instructions and update the GPT.
• "The letter is too long" → Add "Keep all letters under 200 words" to your instructions and save.

Variations

• Simpler version: Skip the Custom GPT and use a standard ChatGPT session with a saved prompt template — takes 5 min instead of 2 but works on the free plan
• Extended version: Add a second GPT for tracking denial patterns — paste denial reasons into it over time and ask "what are the most common denial reasons I'm seeing this month?"

What to Do Next

• This week: Build the GPT, test with your 5 most common denied procedures
• This month: Track your appeal success rate — if a letter type isn't working, refine the system instructions
• Advanced: Create a separate "Peer-to-Peer Request" GPT for supporting radiologist peer-to-peer reviews

Advanced guide for radiologic technologist professionals. Custom GPT requires ChatGPT Plus ($20/mo). AI-generated letters must be reviewed and verified by appropriate clinical staff before submission.