drg 1.0.0

Python MS-DRG grouper — assigns Medicare Severity DRG codes from ICD-10 diagnoses and procedures

drg

Python MS-DRG grouper — assigns Medicare Severity Diagnosis-Related Group codes from ICD-10 diagnoses and procedures.

Implements the CMS MS-DRG algorithm (FY2026 v43.0) as a pure Python package with zero external service dependencies.

Installation

pip install drg

Quick Start

Python API

from drg import MSDRGEngine

engine = MSDRGEngine()

result = engine.group(
    principal_dx="I2109",
    secondary_dxs=["J9601", "E1165"],
    procedures=["02703DZ"],
    age=67,
    sex="M",
)

print(result.drg_code)          # "280"
print(result.description)       # "ACUTE MYOCARDIAL INFARCTION, DISCHARGED ALIVE WITH MCC"
print(result.weight)            # 1.2345
print(result.mdc)               # "05"
print(result.complication_level) # ComplicationLevel.MCC

Command Line

# human-readable output
python -m drg --pdx I2109 --sdx J9601 E1165 --proc 02703DZ --age 67 --sex M

# JSON output
python -m drg --pdx I2109 --json

CLI Flags

Flag	Description	Default
--pdx	Principal ICD-10-CM diagnosis code	required
--sdx	Secondary ICD-10-CM codes (space-separated)	none
--proc	ICD-10-PCS procedure codes (space-separated)	none
--age	Patient age in years	65
--sex	Patient sex (M/F/U)	M
--discharge-status	Discharge status code	01
--json	Output full result as JSON	false
-V / --version	Print version and exit	—

How It Works

The grouper follows the CMS MS-DRG classification logic:

1. Pre-MDC check — transplants, ECMO, tracheostomy, and CAR-T therapy (DRGs 001–019)
2. MDC classification — assigns a Major Diagnostic Category based on the principal diagnosis
3. Surgical/medical partition — determines whether the encounter is surgical (OR procedure present) or medical
4. Complication resolution — evaluates secondary diagnoses for CC/MCC status, applying PDX-based exclusions
5. DRG assignment — selects the final DRG based on MDC, partition, and complication level

API Reference

MSDRGEngine

The main entry point. Data files are lazy-loaded on first call to group().

engine = MSDRGEngine()
result = engine.group(
    principal_dx="I2109",       # ICD-10-CM code (dots optional)
    secondary_dxs=["E1165"],    # secondary ICD-10-CM codes
    procedures=["02703DZ"],     # ICD-10-PCS codes
    age=67,                     # patient age
    sex="M",                    # M/F/U
    discharge_status="01",      # discharge status code
)

GroupingResult

Returned by engine.group(). Key fields:

• drg_code — MS-DRG code (e.g. "282")
• description — DRG description
• mdc — Major Diagnostic Category code (e.g. "05")
• mdc_description — MDC description
• weight — DRG relative weight
• geometric_los — geometric mean length of stay
• arithmetic_los — arithmetic mean length of stay
• partition — PartitionType.SURGICAL or PartitionType.MEDICAL
• complication_level — ComplicationLevel.MCC, .CC, or .NONE
• is_pre_mdc — true for DRGs 001–019
• principal_diagnosis — echoed Diagnosis object
• secondary_diagnoses — echoed list of Diagnosis objects
• procedures — echoed list of Procedure objects
• encounter — echoed Encounter object
• has_or_procedure — true if an OR procedure was detected
• cc_codes_applied — CC codes that contributed to complication level
• mcc_codes_applied — MCC codes that contributed to complication level

Data Sources

This package bundles public domain and open-source reference data:

• CMS FY2026 Final Rule — ICD-10-CM codes, CC/MCC lists, CC exclusions, DRG weights Source: cms.gov License: U.S. government public domain

• Tuva Health — ICD-10-PCS codes, MDC reference, MS-DRG reference Source: github.com/tuva-health/the_tuva_project License: Apache 2.0

Supported Version

• MS-DRG v43.0 (FY2026 Final Rule)
• ICD-10-CM/PCS effective October 1, 2025

Limitations

• Diagnosis-specific DRG families are currently implemented for MDC 04 (respiratory) and MDC 05 (circulatory). Other MDCs fall back to severity-keyword matching against the DRG weights table.
• MDC 24 (multiple significant trauma) is not yet implemented — it requires multi-body-region injury criteria beyond single-PDX classification.
• The grouper covers the most common DRG assignment paths. Edge cases in less common MDCs may produce a fallback result.

Development

git clone https://github.com/tl212/drg.git
cd drg
pip install -e ".[dev]"
pytest

License

Apache 2.0 — see LICENSE.