There are up to three different types of hospital identifiers included in the HCUP databases.

• The data source's own number scheme for identifying hospitals and facilities (DSHOSPID),
• The hospital identifier used by the American Hospital Association (AHAID and IDNUMBER), and
• A unique HCUP hospital identifier (HOSPID).

The hospital entity as defined by the data source may differ from the hospital entity as defined by the AHA. For example, the data source treats two separate facilities as two hospitals, while the AHA Annual Survey treats the two facilities as a single hospital, or vice versa. For consistency across states, HCUP defines hospitals in accordance with the American Hospital Association Annual Survey of Hospitals. During HCUP data processing, the data source's identification of the hospital is reconciled with the identification of the hospital in the AHA Annual Survey of Hospitals. For detailed information about this linking process, see the special report on HCUP Hospital Identifiers.

The HCUP hospital identifier (HOSPID) is based on the AHA hospital identifier and is defined as:

• SSnnn, where SS = State FIPS Code, and
• nnn = hospital number unique to state.

HOSPID is missing for some hospitals because an AHA hospital identifier cannot be determined. Hospitals may not be registered with the AHA or the source-provided information cannot be matched to the AHA.

The data element HOSPID is available in the Hospital file.