Grouper Input Format¶

The group() method accepts a dictionary with the following fields:

{
    "version": 431,
    "age": 65,
    "sex": 0,
    "discharge_status": 1,
    "hospital_status": "NOT_EXEMPT",
    "pdx": {"code": "I5020", "poa": "Y"},
    "admit_dx": {"code": "R0602"},
    "sdx": [
        {"code": "E1165", "poa": "Y"},
        {"code": "I10", "poa": "N"}
    ],
    "procedures": [{"code": "02703DZ"}]
}

Fields¶

Field	Type	Required	Description
`version`	int	Yes	MS-DRG version (400-431). See Versions.
`age`	int	Yes	Patient age in years (0-124)
`sex`	int	Yes	`0`=Male, `1`=Female, `2`=Unknown
`discharge_status`	int	Yes	CMS discharge status code (see below)
`hospital_status`	str	No	`"NOT_EXEMPT"` (default), `"EXEMPT"`, or `"UNKNOWN"`. See Hospital Status.
`tie_breaker`	str	No	`"CLINICAL_SIGNIFICANCE"` (default) or `"ALPHABETICAL"`. See Tie Breaker.
`pdx`	dict	Yes	Principal diagnosis
`admit_dx`	dict	No	Admission diagnosis
`sdx`	list	No	Secondary diagnoses (defaults to `[]`)
`procedures`	list	No	Procedure codes (defaults to `[]`)

Diagnosis format¶

Each diagnosis is a dict with a code and optional poa (Present on Admission) indicator:

{"code": "I5020", "poa": "Y"}  # poa values: "Y", "N", "U", "W"
{"code": "I5020"}               # poa defaults to unchecked

Procedure format¶

Each procedure is a dict with a code:

{"code": "02703DZ"}

Discharge status codes¶

The grouper primarily uses these values for DRG assignment logic:

Code	Description
`1`	Home / Self Care
`20`	Died

Note

Other valid CMS discharge status codes (2–99) are accepted but do not alter grouping behavior in most DRG logic paths. The grouper specifically checks for status 20 (died) which affects certain DRG assignments.

Tie breaker¶

The tie_breaker field controls how secondary diagnoses are prioritized during the marking phase. When multiple SDX codes could match the same DRG formula attribute, this determines which one "wins":

Value	Behavior
`"CLINICAL_SIGNIFICANCE"`	Sort SDX codes: MCC first, then CC, then by ICD code string. Default. Matches CMS Java grouper behavior.
`"ALPHABETICAL"`	Sort SDX codes by ICD code string only.

The CMS Java grouper defaults to CLINICAL_SIGNIFICANCE, which means the most severe diagnosis gets first pick of attribute matches. For example, if both an MCC and a CC diagnosis could contribute to the same formula attribute, the MCC wins and gets marked.

Procedure codes are also sorted by code value when CLINICAL_SIGNIFICANCE is active.