Length of stay (LOS) is calculated by subtracting the admission date (ADATE) from the discharge date (DDATE). Same-day stays are therefore coded as 0. Leave days are not subtracted. Before edit checks are performed, LOS and LOS_X have the same value. If LOS is set to inconsistent (.C), the value of LOS_X is retained.

LOS is not equal to the calculated value in the following cases:

• LOS is set to the supplied length of stay if the length of stay cannot be calculated (ADATE and/or DDATE is missing or invalid). Note: If the supplied length of stay codes same-day stays as 1 or subtracts leave days, then the supplied length of stay is NOT used.
• LOS is missing (.) if the length of stay cannot be calculated and the supplied length of stay is missing.
• LOS is invalid (.A) if
  • it is greater than the maximum value allowed during HCUP processing (the maximum allowed in the 1988-1997 data is 32,767; the maximum allowed beginning in the 1998 data is 20 years)
  • - or -
  • the length of stay cannot be calculated and the supplied length of stay is nonnumeric.
• An invalid calculated LOS is not replaced by the supplied length of stay.
• If the data source does not supply either admission date (ADATE) and discharge date (DDATE), or length of stay, then beginning in the 1998 data LOS is not present on the HCUP files. In the 1988-1997 data, LOS is retained on the HCUP files and is set to unavailable from source (.B).
• LOS is inconsistent (.C) if
  • LOS is negative (ELOS03 beginning in the 1998 data and ED011 in the 1988-1997 data),
  • Excessively long (ELOS04 beginning in the 1998 data and ED601 in the 1988-1997 data), or
  • Charges per day are unjustifiably low (ED911) or high (ED921).

Edit checks ED911 and ED921 are only performed on the 1988-1997 data. No charge per day edit checks are performed on the HCUP data beginning in the 1998 data.