| name | icd10-coding-rules |
| version | 2.0.0 |
| description | Use this skill whenever working on the coding agent, rules engine, CDI agent, DRG calculator, or ANY component that suggests, validates, sequences, or filters ICD-10 codes. Triggers on: ICD-10, ICD10, diagnosis code, coding guideline, Excludes 1, uncertain diagnosis, outpatient vs inpatient coding, POA indicator, combination code, Code First, Use Additional, manifestation code, specificity upgrade, CC/MCC status, or any reference to CMS coding rules. Also use when editing src/core/icd10/, src/agents/coding_agent.py, src/agents/cdi_agent.py, src/prompts/coding_extraction.py, tests/clinical/, or any file that imports from src.core.icd10. If the task involves clinical coding in ANY way, load this skill — even if the user does not explicitly mention ICD-10.
|
| allowed-tools | Read, Bash |
| license | Proprietary |
ICD-10 Coding Rules
Read First
Read references/hard-constraints.md for the 5 rules that
can never be violated (Article II.3 of constitution).
Read references/specificity-upgrades.md for the top 20
revenue-impact specificity upgrades from DISC-002.
Read references/cc-mcc-reference.md for CC/MCC conditions
and DRG tier implications.
Quick Reference — The 5 Hard Constraints
Rule 1: Excludes 1 — Never code together
Two codes with an Excludes 1 relationship cannot appear
in the same claim. Ever.
Check: call mcp_excludes1_check(code_a, code_b) before
suggesting any pair.
Violation consequence: claim denial + FCA exposure.
Rule 2: Outpatient uncertain diagnosis
Qualifier words: possible, probable, suspected, rule out,
working diagnosis, questionable, likely, concern for,
appears to be, consistent with, compatible with, indicative of,
suggestive of, comparable with, still to be ruled out.
Outpatient + any qualifier = code the SIGN or SYMPTOM only.
Never code the uncertain diagnosis as confirmed.
Inpatient = may code as confirmed (Section II.H).
"Ruled out" = eliminated — do NOT code in ANY setting.
OBS status (OBSENC) = OUTPATIENT rules.
Rule 3: Mandatory sequencing (Code First / Use Additional)
Code First / Use Additional instructions are mandatory.
E11.22 (DM with CKD) requires N18.x — cannot code alone.
Use mcp_sequencing_rules(code) to check requirements.
Manifestation codes can NEVER be principal diagnosis.
Rule 4: Combination codes — use them
When a combination code exists for two conditions,
use the combination code. Do not code components separately.
Examples: E11.22 (T2DM with CKD), I11.0 (HTN with HF),
I12.x (HTN with CKD).
Rule 5: POA indicator accuracy
Y = present at admission. N = developed after admission.
U = documentation insufficient. W = clinically undetermined.
ER conditions are POA = Y. Incorrect N on HAC conditions
triggers Medicare payment reduction.
Inpatient vs Outpatient Rules Summary
| Rule | Inpatient | Outpatient |
|---|
| Uncertain diagnosis | Code as confirmed | Code symptom instead |
| Principal diagnosis | Condition chiefly responsible for admission | First-listed = reason for visit |
| POA indicators | Required | Not applicable |
| Chronic conditions | Code if actively managed | Code if addressed |
| "Ruled out" | Do NOT code | Do NOT code |
Encounter class mapping:
- IMP (inpatient) -> INPATIENT rules
- AMB (ambulatory) -> OUTPATIENT rules
- EMER (emergency) -> OUTPATIENT rules
- OBSENC (observation) -> OUTPATIENT rules (critical!)
MCP Tools Available
- mcp_icd10_lookup(code) -> code description, Excludes 1 pairs,
Code First instructions, CC/MCC status, billability
- mcp_icd10_search(term) -> find codes matching a clinical term
- mcp_excludes1_check(code_a, code_b) -> relationship check
- mcp_sequencing_rules(code) -> mandatory pairings
For Full Reference Tables
See references/hard-constraints.md (detailed rule explanations)
See references/specificity-upgrades.md (top 20 upgrades)
See references/cc-mcc-reference.md (CC/MCC conditions)
