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Central Distributor SASD: 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


Beginning in 1995, Maryland supplied an encrypted Medical Record Number. During HCUP processing, this encrypted identifier was assigned to MRN and re-encrypted for MRN_S. Beginning in 1995, MRN_S cannot be matched to MRN_S for earlier years.

In the 2001 SASD, the coding of the source provided medical record number appears inconsistent with other years. Prior to 2001, the supplied values have eleven (11) characters. In 2001, the supplied values have four to nine (4-9) characters. The inpatient and emergency department data provided to HCUP by Maryland include an eleven character medical record number in 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.
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Last modified 4/11/08