User Support

Do Your own analysis
Explore Expert Research & Limited Datasets

Central Distributor SASD: Description of Data Elements

MDID_S - Synthetic attending physician number
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes

For HCUP data from 2001 to 2002, this data element is called MDNUM1_S. Beginning in 2003, this data element is called MDNUM1_R.

MDID_S contains a fixed-key (one-to-one) encryption of the supplied attending physician number (MDID), 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 attending physician and primary surgeon identifiers are the same, the synthetic identifiers, MDID_S and SURGID_S, are the same.
  • When the MDID in the ambulatory surgery data and the inpatient data are the same, the synthetic identifier, MDID_S is the same.

Except in those data sources where physician license numbers are supplied, it is not known whether the physician identifier MDID_S refers to individual physicians or to groups. If the attending 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 MDID_S refers to individual physicians or to groups.

Beginning in the 1993 data, supplied physician identifiers were checked for null characters. If null characters were found, they were replaced by blanks before the identifier was encrypted. Since this conversion was not done in prior years of HCUP data, the encrypted physician identifiers from 1993 on may not match those in earlier years. However, null characters are rarely included.

Uniform Values
VariableDescriptionValueValue Description
MDID_SSynthetic attending physician number16(a)Synthetic physician identifier
State Specific Notes


The attending physician identification number (MDID_S) may not accurately track physicians across hospitals. The state encourages hospitals to use the Professional State License Number as an identifier, but some hospitals continue to use their own internal identification number. Also, some hospitals appear to pad the Professional State License Number (a 5-digit code). Information was not available from the data source about the prevalence of these practices.

Some hospitals may use one license number for all physicians in order to protect physician confidentiality. Information was not available from the data source about the prevalence of this practice.


Florida reports state license numbers for the attending physician identifiers. During HCUP processing, physician identifiers were encrypted (MDID_S).

In 1998, the Florida attending physician numbers (MDID and MDID_S) are truncated. Values that are normally 11 bytes in length, for 1998, are only 10 bytes long. Although it may be difficult to track attending physicians to those before and after 1998, it may still be possible. If 10 bytes match without the 11th byte, it is more than likely the same physician. Primary surgeon numbers (SURGID and SURGID _S) are not affected.


The encrypted attending physician identifier (MDID_S) may not accurately track physicians across hospitals. Kentucky collects two different types of physician identifiers, Universal Physician Identification Numbers (UPINs) and state license numbers.

New Jersey

New Jersey provided state license numbers as physician identifiers for all years.


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.
Are you having problems viewing or printing pages on this website?
If you have comments, suggestions, and/or questions, please contact
Privacy Notice, Viewers & Players
Last modified 4/11/08