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Tuesday, July 28, 2015

Patient Identity Matching without a National Identifier in IHE Profiles

In the US, because Congress won't even let anyone in the Federal government TALK about creating a national identifier (privacy concerns), we have to deal with multiple identifiers at every healthcare provider.  At least in Canada, the provinces can assign a provincial patient ID.  But, not here alas.

So, last week at the IHE Meeting, somebody asked what identifiers are supported in IHE Profiles, from this list.  I think this query may have been in support of this project.

First Name
Last Name
Middle Initial
Date of Birth
Home phone number     
·         Street
·         State
·         Zip
Middle Name
Cell phone
Mothers Maiden Name
Marital Status
Alias or Previous name     
USPS Address
·         Last 4 of SSN
·         Driver License
·         Passport
·         Alien #
Multi Birth
Birth Order
Birth Place
Previous Address
Previous Cell Phone(s)
Insurance ID
Insurance Plan Name
Previous Insurance
Medicaid ID
Medicare ID
Biometric ID

So, I put together a spreadsheet mapping these identifiers to HL7 V2.5.1, PIX, PDQ, PAM, PIX/PDQ V3, XCPD, and PDQm.  It didn't take too long, just a couple of hours.

A quick summary: HL7 Version 2 and PAM supports all of these directly by name with the exception of the alien #, which is simply another identifier in Patient Identifier List (PID-3).  HL7 makes no distinction between current and previous at the field level, although other parameters can be used to distinguish a current address from a previous address, or a current insurance identifier from a previous one. The notion of previous is dependent upon the time the query is performed, rather than being an attribute of any of this data in any case.  The distinction between Alias and simply another name is slim enough that even though PAM doesn't support the alias field, you can use repetitions of the name field to get there.

I don't think race belongs in this list.  It's not an "identifier", because in the US, race is whatever the patient says it is at the time that they say it (see OMB Policy Directive #15), and shouldn't be completed by someone else.

PDQ in all its flavors (V2, V3, and Mobile/FHIR) supports most of these (in bold).  Some (in italics) require the use of the Pediatric Demographics Option.  XCPD is a super set of PDQ V3, so it too supports the same set.

PIX (in all its flavors) performs patient matching.  IHE doesn't specify the algorithm, because master patient directory systems use a variety of different matching algorithms, and these are often tuned to the location where they are used.  Tuning parameters for name matching in Arizona could differ greatly from those in Wisconsin or New York for example.

Any missing pieces could be added as national extensions to existing IHE profiles.


  1. Thanks Keith - this spreadsheet is actually really useful! I appreciate your hard work!

  2. I don't see full SSN? I know it is not always collected and shared, based on local policies and laws, but when it is, it provides the best factor for patient id matching.