The Major Diagnostic Category appropriate for the date of discharge (MDC) is assigned by the Medicare DRG grouper during HCUP processing. Refer to the notes for the data element DRG for complete details.

Labels

Labels for the MDCs are provided as an ASCII file in HCUP Tools: Labels and Formats.

One discharge in 1991 with an invalid principal diagnosis code (DXV1=1) and at least one non-missing secondary diagnosis code (DX2, etc.) had the incorrect DRG and MDC assigned because of a error in HCUP processing. The DRG should have been 470; and the MDC should have been equal to 0.

No other years are affected.

For 2011 data only, HCUP data are modified to comply with confidentiality requirements of the Iowa data Partner:

• Discharges from skilled nursing care or skilled swing beds have the MDC and DRG set to missing
• Discharges that are assigned to MDC 25 during HCUP processing are deleted from the SID.

Some 1989-1990 discharges with a missing principal diagnosis code (DX1=" ") and at least one non-missing secondary diagnosis code (DX2, etc.) have the incorrect DRG and MDC assigned because of an error in HCUP processing. The DRG should be 470; and the MDC should be equal to 0. The following numbers of records are affected:

• 1 record in 1989 and
• 1 record in 1990.

No other years are affected.

Some 1988-1991 discharges with an invalid principal diagnosis code (DXV1=1) and at least one non-missing secondary diagnosis code (DX2, etc.) have the incorrect DRG and MDC assigned because of an error in HCUP processing. The DRG should be 470; and the MDC should be equal to 0. The following numbers of records are affected:

• for 1988, 34 records;
• for 1989, 30 records;
• for 1990, 44 records; and
• for 1991, 33 records.

Beginning with 1992 discharges, DRG and MDC were processed correctly.

According to source documentation, the principal and secondary procedures for one hospital (DSHOSPID="056" and HOSPID=55155) are incorrect in the fourth quarter of 1997. System problems at the hospital caused the last procedure coded on the medical record to be stored as the principal procedure. No secondary procedures were recorded. This affects the DRG, DRG10, MDC, and MDC10 assignment.

Some 1989-1992 discharges with an invalid principal diagnosis code (DXV1=1) and at least one non-missing secondary diagnosis code (DX2, etc.) have the incorrect DRG and MDC assigned because of an error in HCUP processing. The DRG should be 470; and the MDC should be equal to 0. The following number of records are affected:

• for 1989, 23 records;
• for 1990, 4 records;
• for 1991, 1 record; and
• for 1992, 10 records.

Beginning with 1993 discharges, DRG and MDC were processed correctly.