The MS-DRG System: The MS-DRGs range from 001-999, with many unused numbers to accommodate future MS-DRG expansion.
One MS-DRG is assigned to each inpatient stay. The MS-DRGs are assigned using the principal diagnosis and additional diagnoses, the principal procedure and additional procedures, sex and discharge status. Diagnoses and procedures assigned by using ICD-10-CM codes determine the MS-DRG assignment. Accurate and complete ICD-10-CM coding by HIM professionals is essential for correct MS-DRG assignment and subsequent reimbursement.
In the MS-DRG system, many DRGs are split into one, two or three MS-DRGs based on whether any one of the secondary diagnoses has been categorized as an MCC, a CC or no CC.
Example of MS-DRGs with a three way split include:
MS-DRG 539, Osteomyelitis with MCC
MS-DRG 540, Osteomyelitis with CC
MS-DRG 541, Osteomyelitis without CC/MCC
MCC/CC List: Under MS-DRGs, CMS identified those diagnoses whose presence as a secondary diagnosis leads to substantially increased hospital resource use. They then categorized this list into two different levels of severity as follows:
Major complications or comorbidities (MCCs) reflect the highest level of severity
CCs represent the next level of severity.
Some MCCs and CCs are excluded because they are too closely related to the principal diagnoses. This is called the CC Exclusion List and identifies conditions that will not be considered a CC or MCC for a given principal diagnosis. For example, primary cardiomyopathy (425.4) is not a CC for congestive heart failure (428.0).