medical-coding-validator

name	medical-coding-validator
description	Validates medical coding accuracy for ICD-10-CM/PCS, CPT, and HCPCS codes against clinical documentation. Outputs a coding audit with accuracy scores, common error patterns, and correction recommendations.
allowed-tools	Read, Write, WebSearch
effort	medium

Medical Coding Validator

When to activate

When auditing coded claims before submission, reviewing denial patterns, training new coders, or when implementing a new EHR coding module. Use for inpatient, outpatient, and professional fee coding.

When NOT to use

Skip for pre-authorization code estimates (not final coding), patient-facing cost estimates (use patient-intake-optimizer), or when the coding audit was completed within the last 30 days with no system changes.

Instructions

1. Documentation review:

   • Chief complaint and history
   • Assessment and plan (diagnoses with specificity)
   • Procedures performed (approach, devices, body part, qualifier)
   • Time documentation (for E/M level selection)

2. Diagnosis coding (ICD-10-CM):

   • Specificity: Laterality, episode of care, severity
   • Combination codes vs. multiple codes
   • Sequencing: Principal diagnosis first
   • Z-codes for social determinants of health

3. Procedure coding (CPT/ICD-10-PCS):

   • E/M level: MDM complexity or time-based
   • Surgical: Root operation, approach, body part
   • Modifiers: -25 (separate E/M), -59 (distinct procedure), -51 (multiple)

4. Compliance checks:

   • NCCI edits (bundled services)
   • MUE (medically unlikely edits)
   • LCD/NCD coverage policies
   • Documentation supports coded diagnoses

5. Common error patterns to flag:

   • Unspecified codes when specificity is available
   • Upcoding (E/M level higher than documentation supports)
   • Downcoding (missed complexity)
   • Missing Z-codes for social determinants

Output Format

CODING AUDIT: [Encounter type] — [Department/Specialty]
SAMPLE: [X] encounters reviewed | DATE RANGE: [start — end]

ACCURACY:
  Diagnosis (ICD-10-CM): [X]% correct
  Procedure (CPT): [X]% correct
  Modifiers: [X]% correct
  Overall: [X]%

ERRORS FOUND:
| # | Encounter | Code Used | Correct Code | Error Type | Impact |
|---|-----------|-----------|--------------|------------|--------|

COMMON ERROR PATTERNS:
  1. [Pattern] — [Frequency] — [Recommendation]
  2. [...]

COMPLIANCE FLAGS:
  - NCCI edits triggered: [X]
  - MUE exceeded: [X]
  - Documentation gaps: [X]

RECOMMENDATIONS:
  1. [Training focus]
  2. [EHR template change]
  3. [Process improvement]

Example

CODING AUDIT: Outpatient Primary Care — Internal Medicine
SAMPLE: 50 encounters | DATE RANGE: 2026-05-01 to 2026-05-31

ACCURACY:
  Diagnosis (ICD-10-CM): 88% correct
  Procedure (CPT): 82% correct
  Modifiers: 74% correct
  Overall: 81%

ERRORS FOUND:
| # | Encounter | Code Used | Correct Code | Error Type        | Impact      |
|---|-----------|-----------|--------------|-------------------|-------------|
| 1 | ENC-4521  | J06.9     | J06.9 + J02.9| Missing specificity| Undercoded  |
| 2 | ENC-4537  | 99214     | 99215        | MDM supports higher| Undercoded  |
| 3 | ENC-4548  | 99215-25  | 99215        | -25 not supported  | Overcoded   |
| 4 | ENC-4552  | E11.9     | E11.65       | Missing complication| Undercoded |

COMMON ERROR PATTERNS:
  1. Using unspecified codes (E11.9 vs. E11.65) — 12% — Train on diabetes sub-classification
  2. Missing -25 modifier documentation — 8% — Add template prompt for separate E/M

COMPLIANCE FLAGS:
  - NCCI edits triggered: 3 (99214 + 36415 bundled)
  - MUE exceeded: 0
  - Documentation gaps: 4 encounters missing ROS

RECOMMENDATIONS:
  1. Coder training: ICD-10-CM diabetes and respiratory sub-classification
  2. EHR template: Add modifier -25 documentation prompt
  3. Pre-bill audit: Sample 10% of encounters before claim submission