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PNUM_S - Synthetic person number
Documentation Sections:
General Notes
Uniform Values
State Specific Notes
General Notes

Beginning in 2003, this data element is called PNUM_R.

PNUM_S is specific to patients (persons) so that multiple admissions by the same patient can be linked within and across institutions.

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

  • Frequencies of the number of discharges and the number of different hospitals per nonmissing PNUM_S.
  • State-level counts of the number of unique nonmissing PNUM_Ss, the number of discharges associated with these PNUM_Ss, the ratio of these two numbers (discharges/person), and the number of discharges without a PNUM_S.

PNUM_S contains a fixed-key (one-to-one) encryption of the supplied person number (PNUM), 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 the data source codes the same person number inconsistently (sometimes with leading zeros and sometimes with leading blanks), the HCUP person numbers are different.
  • When the PNUM in the ambulatory surgery data and the inpatient data are the same, the synthetic identifier, PNUM_S is the same.

Beginning in the 1993 data, the person 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 person numbers from 1993 on may not match those in earlier years. However, null characters are rarely included.

Uniform Values
VariableDescriptionValueValue Description
PNUM_SSynthetic person number17(a)Person number
State Specific Notes


Due to technical difficulties at the data source, the person number (PNUM and PNUM_S) is not available in Arizona from July 1, 2002 to December 31, 2002. The encrypted person identifier (PNUM_S) may not accurately track patients across hospitals. Arizona accepts social security numbers, health insurance claim numbers, and certificate numbers as person identifiers. No documentation was available about the consistency of coding within and across hospitals.

Beginning in 2003, the supplied person number (PNUM) is length 19 and is inconsistent with the 9-character identifier provided in previous years of data.


California reports encrypted social security numbers as person numbers.


Internet Citation: HCUP Central Distributor SID Description of Data Elements - All States. Healthcare Cost and Utilization Project (HCUP). August 2008. Agency for Healthcare Research and Quality, Rockville, MD.
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Last modified 8/12/08