Prior to 2008, only PRDAY1 is available because Arizona did not report secondary procedure days or dates. Beginning in 2008, Arizona provides dates for all secondary procedures.

Beginning in 1995, only the calculated day of procedure could be used to assign PRDAY because Arizona did not supply the day of procedure. Prior to 1995, no procedure dates or days were reported.

Only the calculated day of procedure could be used to assign PRDAYn because Arkansas did not supply the day of procedure.

Prior to 1998, the supplied day of procedure was not used when PRDAY could not be calculated because California used the same value to indicate no procedure performed and procedure performed on the day of admission.

In 1998 and 1999, only the supplied day of procedure could be used to assign PRDAY because the date of procedure was not provided. A source value of 0 days was set to missing (PRDAYn = .) if there was no corresponding procedure (PRn = " ").

Beginning in 2000, procedure dates were provided by the data source and used to calculate day of procedure.

Beginning in 2010, Colorado began supplying secondary procedure dates. These fields are used to calculate PRDAYn.

Prior to 2010, only PRDAY1 is available because Colorado did not report secondary procedure days or dates.

Only the calculated day of principal procedure could be used to assign PRDAY1 because Colorado did not supply principal procedure day.

Beginning with 2006, Florida provided procedure days for the principal and all secondary procedures.

For 2004 - 2005, only PRDAY1 is available because Florida did not report secondary procedure days or dates.

Through 2003, PRDAY1 is assigned from the supplied day of procedure. Florida did not supply the procedure date for these years. A missing value (.) was assigned from either of the following values supplied by the data source: 998 an indicator that the number of days to procedure is greater than or equal to 998 days; and 999 an indicator of unable-to-compute days, or that no procedure was performed.

Florida also used zeros to code both missing values and a procedure performed on the day of admission. During HCUP processing, PRDAY1 was set to missing (.) if

• the reported procedure day = 0, and
• no principal procedure was reported.

Only the calculated day of procedure could be used to assign PRDAYn because Hawaii did not supply the day of procedure.

Prior to 2010, only PRDAY1 is available because Indiana did not report secondary procedure days or dates. Beginning in 2010, Indiana started supplying secondary procedure dates.

Only the calculated day of procedure could be used to assign PRDAYn because Indiana did not supply this information.

Only the calculated day of procedure could be used to assign PRDAY because Iowa did not supply the day of procedure.

Beginning with 2005, Kansas provided procedure dates, which were used to calculate day of procedure.

Prior to 2005, no procedure days or dates were reported.

Only the calculated day of procedure could be used to assign PRDAYn because Maine did not supply procedure days.

Beginning in 2013, the HCUP Maryland SID includes 30 procedure days. Previously, the HCUP Maryland SID included 11 procedure days (PRDAYn).

Beginning with October 2006, PRDAY4-15 were calculated during the HCUP data processing.

Beginning with October 2006, Massachusetts provided procedure dates for all procedure fields.

From 2003 through Sept 2006, Massachusetts supplied three procedure date fields.

Prior to 2003, the supplied day of procedure was not used when PRDAYn could not be calculated because Massachusetts used the same value to indicate no procedure performed and procedure performed on the day of admission.

Prior to 2007, only PRDAY1 is available because Michigan did not report secondary procedure days or dates.

Only the calculated day of procedure could be used to assign PRDAYn because Minnesota did not supply day of procedure.

Only the calculated day of procedure could be used to assign PRDAYn because Nebraska did not supply day of procedure.

Beginning in 2008, Nevada supplied secondary procedure dates.

Prior to 2008, only PRDAY1 is available.

Only the calculated day of procedure could be used to assign PRDAY because New Jersey did not supply the day of procedure.

In the 1988-1997 HCUP New York databases, PRDAYn could not be calculated because New York did not report full admission and procedure dates. During HCUP processing, only the reported procedure day could be used to assign PRDAYn. For 1988-1992, the source miscalculated procedure days for records with admission dates in the year prior to discharge, resulting in procedure days that were not during the stay. These records failed the appropriate edit check. Beginning in 1993, the source correctly calculated procedure days for all procedures.

Beginning with the 2008 data, the HCUP data element PRDAYn is missing (.) for AIDS/HIV patients. New York identifies AIDS/HIV records by ICD-9-CM diagnosis code, DRG, or MS-DRG:

• An admitting, principal or any secondary diagnosis of "042", "043", "044", "7958", "27910", "27919", "2793", "1363", "79571", "07951", "07952", "07953", "V017" or "V08".
• A DRG of 488 through 490 (prior to October 2007) or MS-DRG of 700 through 716 (beginning in October 2007).

Please note that the admitting diagnosis is not retained in the HCUP databases prior to 2012.

Only the reported day of procedure could be used to assign PRDAYn because North Carolina did not supply procedure dates.

Only the calculated day of procedure could be used to assign PRDAYn because Oregon did not supply procedure days.

Only the calculated day of procedure could be used to assign PRDAYn because Rhode Island did not supply day of procedure.

Only the calculated day of procedure could be used to assign PRDAYn because South Carolina did not supply the day of procedure.

Only the calculated day of procedure could be used to assign PRDAYn because South Dakota did not supply day of procedure.

Beginning with 1998, only PRDAY1 is available because Wisconsin did not report secondary procedure days or dates.

Until 1997, PRDAYn could not be calculated because Wisconsin did not report procedure dates. During HCUP processing, only the reported procedure day could be used to assign PRDAYn. Beginning in 1997, Wisconsin provided the date of principal procedure (PRDATE1).

Principal procedure day is only required for major procedures (defined below). Procedure days are set to missing for all other cases.

Major procedures are defined as Class 1 or 2 procedures. The UHDDS system grouped ICD-9-CM procedure codes into four classes differentiated by impact on either the well-being of the patient or on the health care system. The criteria used to classify procedures included procedural risk, anesthetic risk, and the need for highly trained personnel, special facilities or special equipment. The classes are:

• Class 1: Surgical
• Class 2: Significant procedure (date required)
• Class 3: Significant procedure (date not required)
• Class 4: Minor procedures not normally coded on inpatient data