CMS MS-DRG Definitions Manual v42.0

CMS MS-DRG Definitions Manual v42.0 — FY 2025

Medicare Severity Diagnosis Related Group Grouper Logic

Document Scope

This manual defines the logic used by the CMS MS-DRG Grouper software to assign inpatient hospital claims to Medicare Severity Diagnosis Related Groups (MS-DRGs) for payment under the Inpatient Prospective Payment System (IPPS). 1

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🔑 Core Components

1. MS-DRG Structure Overview

Total MS-DRGs in v42.0: 775 [[1]]
├── Medical DRGs (designated "M")
├── Surgical DRGs (designated "P") 
└── Subdivisions by:
    ├── MCC (Major Complication/Comorbidity)
    ├── CC (Complication/Comorbidity)  
    └── Without CC/MCC

2. MDC (Major Diagnostic Category) Framework

MDC	Body System/Condition	DRG Range
01	Diseases & Disorders of the Nervous System	020-042
02	Diseases & Disorders of the Eye	113-125
03	Diseases & Disorders of the Ear, Nose, Mouth & Throat	126-159
04	Diseases & Disorders of the Respiratory System	163-208
05	Diseases & Disorders of the Circulatory System	209-317
06	Diseases & Disorders of the Digestive System	326-446
07	Diseases & Disorders of the Hepatobiliary System & Pancreas	447-456
08	Diseases & Disorders of the Musculoskeletal System & Connective Tissue	457-516
09	Diseases & Disorders of the Skin, Subcutaneous Tissue & Breast	517-535
10	Endocrine, Nutritional & Metabolic Diseases & Disorders	536-643
11	Diseases & Disorders of the Kidney & Urinary Tract	650-707
12	Diseases & Disorders of the Male Reproductive System	708-714
13	Diseases & Disorders of the Female Reproductive System	715-761
14	Pregnancy, Childbirth & the Puerperium	765-800
15	Newborns & Other Neonates	789-799
16	Diseases & Disorders of Blood, Blood Forming Organs & Immunologic Disorders	800-808
17	Myeloproliferative Diseases & Disorders, Poorly Differentiated Neoplasms	809-829
18	Infectious & Parasitic Diseases	830-849
19	Mental Diseases & Disorders	870-887
20	Alcohol/Drug Use or Induced Mental Disorders	888-897
21	Injuries, Poisonings & Toxic Effects of Drugs	898-909
22	Burns	910-923
23	Factors Influencing Health Status & Other Contacts with Health Services	927-947
24	Multiple Significant Trauma	948-951
25	HIV Infections	955-959
PRE-MDC	Pre-MDC Assignments (e.g., tracheostomy, ECMO, transplant)	001-019

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⚙️ Grouper Logic Flow

graph TD
    A[Claim Input] --> B{Pre-MDC Assignment?}
    B -->|Yes: Trach/ECMO/Transplant | C[Assign Pre-MDC DRG]
    B -->|No | D[Assign to MDC via Principal Dx]
    D --> E{Surgical Procedure Present?}
    E -->|Yes | F[Assign to Surgical DRG within MDC]
    E -->|No | G[Assign to Medical DRG within MDC]
    F & G --> H{Secondary Dx: MCC?}
    H -->|Yes | I[Assign DRG with MCC]
    H -->|No | J{Secondary Dx: CC?}
    J -->|Yes | K[Assign DRG with CC]
    J -->|No | L[Assign DRG without CC/MCC]
    I & K & L --> M[Final MS-DRG Output]

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📋 CC/MCC Designation Rules

Definition Framework 24

Designation	Definition	Impact
MCC	Major Complication/Comorbidity: Represents end-of-life, organ failure, advanced systemic decompensation, or conditions requiring ICU-level care	Highest payment weight; typically adds $8K-$20K reimbursement
CC	Complication/Comorbidity: Chronic illness with exacerbation risk, post-procedure impact, or conditions requiring increased nursing/monitoring	Moderate payment weight; typically adds $3K-$8K reimbursement
Non-CC	Conditions not meeting CC/MCC criteria or not present on admission	No additional payment adjustment

The Nine Guiding Principles for CC/MCC Analysis 6

1. Represents end-of-life/near death or advanced systemic decompensation
2. Denotes organ system instability or failure
3. Involves chronic illness with susceptibility to exacerbations
4. Serves as marker for advanced disease across multiple comorbidities
5. Reflects systemic impact
6. Postoperative/post-procedure condition impacting recovery
7. Requires higher level of care (ICU, intensive monitoring, extended LOS)
8. Impedes patient cooperation or care management
9. Recent change in best practice affecting resource use

FY 2025 CC/MCC List Updates 2224

+ ADDED TO MCC LIST (4 codes):
+ T36-T50 poisoning codes with specific intent + complication
+ Selected sepsis codes with organ dysfunction specificity
 
+ ADDED TO CC LIST (29 codes):
+ Expanded CKD staging codes
+ Additional malnutrition severity codes  
+ New respiratory failure subtypes
+ Selected post-procedural complication codes
 
- DELETED FROM CC/MCC LISTS:
- Codes merged into combination codes
- Obsolete terminology updates

CC/MCC Query Trigger

When documentation states a condition but lacks severity specificity (e.g., “malnutrition” without “severe/moderate”), query the provider. CC/MCC designation often hinges on explicit severity language.

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🧩 Key Logic Tables (Reference)

POA (Present on Admission) Indicator Rules

POA Value	Meaning	CC/MCC Impact
Y	Present at time of inpatient admission	Eligible for CC/MCC if meets criteria
N	Not present at admission (developed during stay)	May still qualify if impacts care, but flagged for HAC review
U	Documentation insufficient to determine	Treated as “N” for payment purposes
W	Clinically undetermined	Provider must clarify; may require query
1	Exempt from POA reporting	Unaffected by POA logic (e.g., external cause codes)

Procedure Code (ICD-10-PCS) OR vs. Non-OR Designation

Operating Room (OR) Procedures:
• Require specialized equipment, anesthesia, or surgical suite
• Typically drive assignment to surgical DRGs
• Examples: 0DTJ8ZZ (resection), 0YU64JZ (bypass)

Non-Operating Room (Non-OR) Procedures:
• Performed at bedside, clinic, or minor procedure room
• May still affect DRG if "significant procedure" per CMS logic
• Examples: 3E0U33Z (transfusion), 4A023N6 (dialysis)

MCE (Medicare Code Editor) Edits Applied Pre-Grouper

1. Diagnosis/Procedure Age/Sex Edits - Reject biologically implausible codes
2. POA Logic Edits - Flag HACs (Hospital-Acquired Conditions) for payment adjustment
3. Unacceptable Principal Diagnosis Edits - Prevent symptom codes as principal dx
4. Procedure/Diagnosis Inconsistency Edits - Flag clinical mismatches
5. Multiple Birth/Newborn Edits - Special logic for obstetric/neonatal claims

MCE Edits Are Mandatory

Claims failing MCE edits are rejected pre-payment. Always run claims through MCE logic before submission.

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🔄 FY 2025 Notable DRG Changes

New DRGs Created

DRG	Title	MDC	Clinical Rationale
317	Concomitant Left Atrial Appendage Closure and Cardiac Ablation	05	Recognize resource intensity of combined structural heart procedures
426-428	Multiple Level Significant Trauma with MCC/CC/without	PRE-MDC	Better stratify polytrauma cases previously grouped broadly

DRGs Deleted

DRG	Title	Reason for Deletion
453	Combined Anterior/Posterior Spinal Fusion w/ MCC	Merged into revised spinal fusion DRGs
454	Combined Anterior/Posterior Spinal Fusion w/ CC	Consolidated for clinical coherence
455	Combined Anterior/Posterior Spinal Fusion w/o CC/MCC	Streamlined spinal procedure logic

Title/Logic Modifications

• DRG 276: Renamed to “Cardiac Defibrillator Implant with MCC or Carotid Sinus Neurostimulator” to include BAROSTIM™ system cases 9
• Cardiac Ablation Codes: Refined list of ICD-10-PCS codes mapping to ablation DRGs for precision
• LAAC Procedure Codes: Added 9 new ICD-10-PCS codes for left atrial appendage closure procedures

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📥 Using the Manual: Practical Workflow

Step 1: Verify Principal Diagnosis Assignment

✅ Does the principal dx represent the condition established *after study* as chiefly responsible for admission? [[6]]
✅ Is it sequenced per UHDDS guidelines?
✅ Does it map to a valid MDC?

Step 2: Identify Surgical Procedures

✅ Are any ICD-10-PCS procedures reported?
✅ Are they designated OR or Non-OR per CMS logic?
✅ Do they trigger Pre-MDC assignment (e.g., tracheostomy, ECMO)?

Step 3: Evaluate Secondary Diagnoses for CC/MCC

✅ Does each secondary dx meet clinical significance criteria?
✅ Is severity explicitly documented (e.g., "acute," "severe," "with organ dysfunction")?
✅ Is POA status correctly assigned (Y/N/U/W)?
✅ Does the dx appear on the official CC/MCC list for FY 2025?

Step 4: Run Through Grouper Logic

✅ Input codes into MS-DRG Grouper v42.0 software or validated encoder
✅ Review MCE edit warnings and resolve before submission
✅ Confirm final DRG assignment aligns with clinical picture

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🔗 Related Vault Notes

• ICD-10-CM Official Guidelines FY 2025
• CC-MCC Reference List FY2025
• POA Reporting Guidelines
• MCE Edit Resolution Checklist
• Query Writing Templates for Clinical Validation

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📚 Official Resources

• CMS MS-DRG Classifications Portal 2
• ICD-10 MS-DRG v42.0 Definitions Manual (Full Text) 3
• FY 2025 IPPS Final Rule (CMS-1808-F)
• CC/MCC Master Lists FY 2025 24

Bottom Line

The MS-DRG Definitions Manual v42.0 is the source of truth for inpatient payment logic. Mastery requires understanding: (1) MDC assignment via principal diagnosis, (2) surgical vs. medical DRG branching, (3) CC/MCC stratification rules, and (4) MCE pre-processing edits. Always validate against the official CMS software or a CMS-certified encoder.

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Last synced: $(date)
Next review: FY 2026 IPPS Proposed Rule (expected July 2025)