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Central Distributor SEDD: Description of Data Elements

MRN_S - Synthetic medical record number
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes

Beginning in 2003, this data element is called MRN_R.

MRN_S is specific to patients (persons) so that multiple admissions by the same patient to a single institution can be linked. MRN_S does not allow linkage of persons across institutions.

MRN_S should not be used for analyses without first consulting summary statistics on:

  • Frequencies of the number of discharges per nonmissing MRN_S, by hospital, and
  • Hospital-level counts of the number of unique nonmissing MRN_Ss, the number of discharges associated with these MRN_Ss, the ratio of these two numbers (discharges/person), and the number of discharges without a MRN_S.

MRN_S contains a fixed-key (one-to-one) encryption of the supplied medical record number (MRN), 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 retained. If a hospital codes the same medical record number inconsistently (sometimes with leading zeros and sometimes with leading blanks), the HCUP medical record numbers are different.
  • When the MRN in the ambulatory surgery data and the inpatient data are the same, the synthetic identifier, MRN_S is the same.

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

Uniform Values
VariableDescriptionValueValue Description
MRN_SSynthetic medical record number17(a)Synthetic medical record number
State Specific Notes


Caution should be used when using MRN_S to track patients back to 1999. The values supplied by the data source in the 1999 data appear different from the values supplied beginning in 2000.

Maine provides encrypted medical record numbers. During HCUP processing, medical record numbers were re-encrypted (MRN_S).


Internet Citation: HCUP Central Distributor SEDD Description of Data Elements - All States. Healthcare Cost and Utilization Project (HCUP). September 2008. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 9/11/08