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.