Three HCUP data elements contain information on the source of admission:

• ASOURCEUB92 (available beginning in 2002 data) indicates the source of admission and uses the same coding as the source of admission data element on the UB-92 claim form. ASOURCEUB92 has more detailed categories for routine admissions and transfers from other health facilities than the HCUP data element ASOURCE. Some states do not provide enough detail in the coding of the source of admission to accurately code ASOURCEUB92. For these states, the data element ASOURCEUB92 is not available.
• ASOURCE (available for all data years) indicates the source of the admission (emergency department; transfer from a hospital; routine, birth and other; etc.) recoded into HCUP uniform values. Routine, birth, and other (ASOURCE=5) include referrals from physicians, clinics, and HMOs. Transfer from a hospital may include transfers within the same hospital as well as transfers between hospitals. If the data source does not provide the admission source, then beginning in the 1998 data, ASOURCE is not present on the HCUP files. In the 1988-1997 data, ASOURCE is retained on the HCUP files and is set to unavailable from source (.B).
• ASOURCE_X (available beginning in 1998 data) retains the source of admission as provided by the data source. The original values have not been recoded into uniform HCUP values and are source-specific. ASOURCE_X is available for all states that provide HCUP with information on admission source.