Challenges and Limitations of General-Purpose Large Language Models in Medical Coding Accuracy and Domain-Specific Requirements

Medical coding means changing patient diagnoses, procedures, and services into standard codes like ICD-10-CM, CPT, and SNOMED CT. These codes are important for billing, payments, reporting, and analysis in U.S. healthcare. Getting the codes right is very important to get proper payments and follow rules like HIPAA and Medicare. But medical coding is hard because medical terms are complex, coding rules change often, and codes must fit the specific situation.

For hospital leaders, clinic owners, and IT managers in the U.S., making sure coding is correct while keeping costs down is always a challenge. Using AI to help with coding can cut down on manual work, lower mistakes, and improve how money flows. But picking the right AI tool means knowing what each tool can and cannot do.

Limitations of General-Purpose Large Language Models in Medical Coding

General LLMs like GPT-3.5 and GPT-4 can understand and write natural language well. They learned from many kinds of books, articles, and websites, so they can create text for many topics and languages. But they don’t have the deep medical knowledge needed for exact medical coding.

A 2023 study by Mount Sinai showed that basic LLMs got only about 34% exact matches for ICD-10 codes and 50% for CPT codes. This happened because of several problems:

  • Lack of Domain-Specific Knowledge: These LLMs know general topics but not detailed clinical terms like ICD-10-CM, SNOMED CT, or CPT. They often do not get the fine meanings of medical language, which causes mistakes.
  • Hallucinations and False Coding: LLMs sometimes make up wrong or unrelated codes because they guess based on patterns, not verified coding rules.
  • Insufficient Handling of Ambiguities: Many medical terms can mean different things depending on the context. General LLMs cannot always figure this out and may code inconsistently.
  • Ethical and Safety Concerns: Wrong codes can affect payments and patient care, raising worries about relying on AI for clinical notes.

Dr. Jingqi Wang from IMO Health said that without specific medical knowledge, these models “struggle with medical coding accuracy and often make wrong or fake codes.” This happens even with big models and lots of training because they lack medical rules and guidelines.

Also, general LLMs can’t always tell real facts from made-up information or follow the many coding rules needed to meet U.S. laws and financial rules in healthcare.

Domain-Specific Requirements to Improve Medical Coding Accuracy

To work better, medical coding AI needs to use special medical knowledge and data. IMO Health, a company that works with clinical terms and AI coding, showed that adding deep clinical knowledge to LLMs makes coding much more accurate.

1. Integration of Clinical Terminologies and Ontologies

Systems like ICD-10-CM, CPT, SNOMED CT, LOINC, and RxNorm are the base for medical coding in the U.S. IMO Health’s terminology covers millions of clinical ideas in 24 areas and has about 20% more synonyms than the Unified Medical Language System (UMLS). This helps the AI match terms with the right codes.

When these terminologies are part of the AI, it better understands medical vocabulary used in U.S. healthcare. This leads to much higher exact coding accuracy—IMO Health reports up to 92% accuracy for ICD-10-CM, while generic LLMs get only 34-55%.

2. Use of Proprietary Knowledge Layers and Editorial Guidelines

IMO Health adds special editorial guidelines and mapping rules developed over many years. Experts with more than 440 years of combined experience contribute to this knowledge base.

This knowledge limits AI from making up wrong codes by only allowing codes that follow industry and insurer rules. It also helps create extra codes and scores for risk adjustment and value-based care payment methods used in the U.S.

3. Advanced AI Techniques: Fine-Tuning, Prompt Engineering, and Retrieval-Augmented Generation (RAG)

Fine-tuning LLMs with carefully labeled clinical data helps them understand medical language better for coding. IMO Health’s AI experts use prompt engineering to add 22 coding rules directly into the AI’s instructions. This guides the AI to follow the rules.

Retrieval-augmented generation (RAG) lets the AI check trusted terminology databases in real time. Instead of just guessing codes, the AI selects from verified options. This lowers mistakes, makes AI decisions clearer, and reduces costs because the AI is used only when needed.

By using LLMs only for complex cases and coding simple ones directly, accuracy improves from 82.9% to 90%, and computing costs go down.

4. Data Quality and Compliance with U.S. Standards

Good, standard data is needed for AI to learn and work well in medical coding. IMO Health follows United States Core Data for Interoperability (USCDI) version 4 and will through at least 2028 to meet U.S. rules.

Data is handled to protect patient privacy following HIPAA, providing clean and safe data for AI training and testing.

AI and Workflow Automations in Medical Coding for U.S. Practices

AI is improving not just coding accuracy but also daily healthcare office work and money cycle processes. IT leaders and practice managers find that AI automation can cut down on administrative work and make daily tasks easier.

Companies like Simbo AI focus on automating patient calls and answering services. This supports backend coding automation by managing patient communication and front-office tasks.

Front Office Automation and Patient Interaction

Simbo AI uses conversational AI to handle patient calls, schedule appointments, and answer basic questions. This reduces the work for staff and keeps communication steady and on time without needing humans.

Good front-office automation helps avoid appointment mistakes and supports patient satisfaction, which indirectly helps with accurate coding by making sure visits and procedures are recorded and scheduled correctly.

Integration with Medical Coding Solutions

When AI handles patient contacts and coding well, doctors and coders can focus on care and complicated cases. Combining domain-specific AI with workflow automation that links to Electronic Health Records (EHRs) and practice software reduces documentation mistakes that hurt coding.

Cost Efficiency and Resource Optimization

AI automation lowers operational costs by managing routine communication and data work. Automating simple coding and front-office tasks helps healthcare groups use staff better and speeds up claim submissions and payments.

Enhancing Data Accuracy and Compliance

Automated workflows include built-in compliance checks and standard documentation steps during patient registration and visits. This reduces human mistakes and missing information that can complicate coding and helps meet U.S. rules.

Practical Considerations for U.S. Medical Practices

Healthcare leaders thinking about AI for coding and automation should consider these points:

  • Domain-Specific AI Investment: AI must include clinical terms and mapping rules to meet accuracy and rule-following needs. Basic LLMs can’t replace human coders or workflows without serious medical focus.
  • Integration with Existing Systems: AI tools need to connect well with EHRs, practice systems, and billing software in U.S. settings. Following standards like USCDI helps smooth data sharing.
  • Staff Training and Oversight: Even with AI, human experts must check coding results. Explainable AI, like IMO Health’s models, gives reasons for code choices to help spot and fix errors.
  • Cost-Benefit Analysis: Using LLMs only for hard cases saves money by cutting expensive computing. Automating front-office tasks lowers staff costs and improves patient experience.
  • Regulatory Compliance and Data Privacy: AI solutions must follow HIPAA rules and protect patient data in how it is stored and used.
  • Continuous Monitoring and Updates: AI tools for coding need regular updates to keep up with changing coding rules, payments, and clinical guidelines.

Summary of Key Statistics and Insights

  • General LLMs like GPT-4 get about 34% exact match accuracy for ICD-10 and 50% for CPT codes in medical coding tasks.
  • IMO Health’s own knowledge base, with clinical terms and AI methods, raises ICD-10-CM coding accuracy to 92%.
  • About 89% of U.S. doctors, nurses, and physician assistants use IMO Health’s terminology, showing wide acceptance.
  • Using LLMs only for complex cases with retrieval-augmented generation improves coding accuracy by over 7% and cuts costs.
  • Advanced prompt methods that include coding rules guide AI toward compliance and accuracy.
  • Including Hierarchical Condition Category (HCC) scores in AI helps with risk adjustment and value-based care payments.
  • Bloomberg’s work shows that high-quality, focused data and fine-tuning are needed to build useful healthcare LLMs.

Final Thoughts for Healthcare Leaders in the United States

Using AI in medical coding means understanding that large general LLMs alone do not meet U.S. accuracy and compliance needs. Adding clinical terms, editorial rules, and fine-tuning is necessary.

Healthcare groups that pick AI coding solutions should focus on clear explanations, good data, and following rules to improve revenue and coding quality. Combining coding AI with front-office automation like Simbo AI’s phone systems offers a practical way to make healthcare work better, faster, and cheaper.

Balancing technology with skilled human checks can help U.S. medical practices improve coding accuracy, get proper payments, and keep good patient care records as healthcare keeps changing.

Frequently Asked Questions

What challenges do general-purpose LLMs face in medical coding?

General-purpose LLMs struggle with accuracy, often producing errors without domain-specific support. They lack the specialized training on clinical terminology required for precise medical coding, leading to imprecise or even falsified code generation.

How does integration of clinical terminology improve LLM performance in medical coding?

Incorporating structured, domain-specific clinical terminology enhances LLMs by providing rich, standardized vocabularies and mapping logic, which significantly improves coding precision, reliability, and reduces errors compared to out-of-the-box LLMs.

What role does IMO Health’s knowledge layer play in enhancing AI-powered coding?

IMO Health’s knowledge layer combines advanced clinical terminologies, editorial guidelines, mapping logic, and AI tools to fine-tune LLMs, producing highly accurate, explainable, and trustworthy medical coding outputs that align with clinical practice.

How effective are IMO Health’s AI-enhanced models compared to standard LLMs?

The IMO Health AI solution achieves up to 92% accuracy on ICD-10-CM coding, outperforming standard LLMs that reach only about 55% accuracy, demonstrating considerable improvement in medical coding precision.

What AI techniques does IMO Health use to optimize LLMs for medical coding?

IMO Health utilizes advanced prompt engineering, retrieval augmented generation (RAG), fine-tuning with curated datasets, and AI agent orchestration to improve coding accuracy, reduce hallucinations, and increase explainability.

What is Retrieval Augmented Generation (RAG) and its benefit in medical coding?

RAG enables LLMs to retrieve relevant clinical codes from IMO Health’s terminology APIs, reducing hallucinations and errors by narrowing code generation to selecting pre-existing candidates, thus boosting accuracy and lowering computational costs.

How do AI agents support explainability and trust in coding outputs?

AI agents built on LLMs call upon IMO Health’s tools and APIs for terminology normalization and guidelines, transforming coding from a black-box output to an explainable process with clear rationale, increasing coder trust and acceptance.

How does IMO Health ensure data quality for AI medical coding?

IMO Health maintains a curated, comprehensive clinical terminology with updated mappings and editorial guidelines driven by decades of expert clinical informatics experience, ensuring clean, standardized data for reliable AI model training and usage.

What cost-efficiency benefits arise from combining IMO Health’s knowledge layer with LLMs?

By pre-processing and covering most diagnoses through terminology alone and selectively engaging LLMs for complex cases, the solution optimizes resource use, improves overall accuracy by over 7%, and significantly lowers operational costs in medical coding workflows.

How does integrating Hierarchical Condition Category (HCC) scores improve revenue and care management?

Incorporating HCC scores into AI coding automates accurate risk adjustment coding critical to value-based care reimbursements, streamlining workflows, increasing revenue capture, and enhancing population health analytics without manual efforts.