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Central Distributor SASD: Description of Data Elements

MDNUM3_S - Synthetic third physician number
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes

HCUP encrypted physician identifiers are referred to by different names in the HCUP data across years.

Year Variable
1988-2000 MDID_S
2001-2002 MDNUM1_S
Beginning with 2003 MDNUM1_R

MDNUM3_S contains a fixed-key (one-to-one) encryption of the supplied third physician number (MDNUM3_S), according to the following rules:

  • All alphanumeric digits are used in the encryption.
  • All symbols such as ".,:;'*@" are retained in the encrypted value, but not in the same location.
  • Leading zeros are encrypted so that the two original physician identifiers "000A6" and "A6" are distinctly different.
  • When the original physician identifiers are the same, the synthetic identifiers, MDID_S, SURGID_S and MDNUM3_S, are the same.
  • When the MDNUM3_S in the ambulatory surgery data and the inpatient data are the same, the synthetic identifier, MDNUM3_S is the same.

Except in those data sources where physician license numbers are supplied, it is not known whether the physician identifier MDNUM3_S refers to individual physicians or to groups. If the physician numbers supplied by the data source are not restricted to license numbers, the state-specific note includes available information about reporting practices, including whether MDNUM3_S refers to individual physicians or to groups.

Supplied physician identifiers were checked for null characters. If null characters were found, they were replaced by blanks before the identifier was encrypted.

Uniform Values
VariableDescriptionValueValue Description
MDNUM3_SSynthetic third physician number16(a)Synthetic physician identifier
State Specific Notes


Beginning in 2017, Kentucky replaced the two consulting practitioner NPI numbers by the referring practitioner NPI (HCUP MDNUM3) and the patient's family practitioner NPI (HCUP MDNUM4).

Beginning in 2012, Kentucky supplies two additional consulting practitioner NPI numbers that are saved as HCUP data element MDNUM3 and MDNUM4.

Beginning October 2009, only NPIs accepted as valid IDs for both facilities and clinicians.

  1. Attending physician is provided in MDNUM1_S and
  2. Physician that performed the primary procedure is provided in MDNUM2_S.

Physician identification numbers may not accurately track physicians within and across hospitals. Kentucky collects two different types of physician identifiers, National Provider Identifier (NPI) and state license numbers.


Internet Citation: HCUP Central Distributor SASD Description of Data Elements - All States. Healthcare Cost and Utilization Project (HCUP). April 2008. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 4/11/08