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MS-DRG grouper

The Medicare Severity DRG (MS-DRG) grouper is an updated version of the original CMS Diagnosis Related Groups (DRGs). Like CMS DRGs, MS-DRGs are a set of inpatient classifications that relate a hospital’s case mix to resource demands and associated costs. With the original grouper, one DRG was assigned to a patient record based on ICD-9-CM codes identifying principal diagnosis, secondary diagnoses, and surgical procedures. Other relevant factors included age, sex, and discharge status.

In 2007, when the name of the v25.0 grouper was changed to MS-DRGs, the logic had evolved to also account for complications and comorbidities (CCs) and hospital-acquired conditions (HACs).

In October 2015, the MS-DRG grouper was updated to classify inpatients into clinically similar groups based on ICD-9-CM or ICD-10-CM/PCS diagnosis and procedure codes.

The MS-DRG grouper is used specifically for Medicare patients. It is updated annually, generally on October 1, and the discharge date of the patient record determines which version of the grouper should be used.

(For non-Medicare grouping, see APR DRGs.)

Medicare Severity DRG (MS-DRG) grouper

Also named



Centers for Medicare & Medicaid Services (CMS)

Developed by 3M HIS under contract with CMS


October 1, 2007

Significant modification and renaming of CMS DRG v25.0


Newest version of CMS DRGs, serving as the basic unit of payment in Medicare's inpatient hospital reimbursement system.

Patient type


Based on

CMS DRG grouper

Codes used

ICD-9-CM diagnosis and procedure codes

ICD-10 codes, starting with v28


AP-DRG grouper

APR DRG grouper

You can find a detailed description of the logic and a history of the development of the CMS DRG and MS-DRG groupers in the current Medicare Severity DRG Definitions Manual available through

See also

Grouper reference topics

AP-DRG grouper

APC grouper

APG grouper

APR DRG grouper

EAPG grouper

Medicare ASC grouper

TRICARE Outpatient grouper