In the HCUP inpatient databases, the admitting ICD-10-CM diagnosis is retained in the variable I10_DX_Admitting. In HCUP outpatient data, the reason for the patient's visit is retained in up to three variables (I10_DX_VISIT_REASON1 â I10_DX_VISIT_REASON3).
Diagnoses are compared to a list of ICD-10-CM codes valid for the discharge date. Anticipation of or lags in response to official ICD-10-CM coding changes are permitted for discharges occurring within a window of time around the official ICD-10-CM coding changes (usually October 1). A year window (six months before and six months after) is allowed. Invalid diagnoses are set to "invl".
For data prior to the fourth quarter of 2015, the admitting diagnosis is stored in the data element DX_Admitting to indicate the use of the ICD-9-CM coding system.