Patients are assigned to an ungroupable MS-DRG if certain types of medical records errors which may affect MS-DRG assignment are present. Patients with an invalid or non-existent ICD-10-CM code as principal diagnosis will be assigned to the ungroupable MS-DRG.

What does an Ungroupable DRG mean?

Diagnosis-related group (DRG) is a system to classify hospital cases into one of originally 467 groups, with the last group (coded as 470 through v24, 999 thereafter) being "Ungroupable". ... The system is also referred to as "the DRGs", and its intent was to identify the "products" that a hospital provides.

What is DRG reimbursement based on?

DRG payment is based on the care given to and resources used by a "typical" patient within the group. When the cost of treating a specific patient is unusually high compared to a typical patient in the same DRG classification, the case is referred to as an outlier.