HL7 PID Segment: Fields, CX/XPN & FHIR Patient

The HL7 `PID` segment (Patient Identification segment) is the foundational patient demographic and identity segment defined in Chapter 3 (Patient Administration) of the HL7 Version 2.x messaging standard. Across virtually every patient-centric HL7 v2 message type—including Admission, Discharge, and Transfer (`ADT`), Order (`ORM`/`OMG`), Observation Result (`ORU`), Scheduling (`SIU`), Immunization (`VXU`), and Financial (`DFT`) feeds—the `PID` segment immediately follows the message header (`MSH` and optional `EVN`) to establish Enterprise Master Patient Index (EMPI) linkage during patient registration, laboratory result routing, and clinical trial data integration.

What Is the HL7 PID Segment? Core Fields (`PID-1` Through `PID-30`) Explained

In HL7 v2.5.1 through v2.8.2, the `PID` segment contains up to 39 pipe-delimited (`|`) fields, of which fields `PID-1` through `PID-30` carry the core demographic, identity, and mortality attributes used in hospital interface engines and HL7 parsers:

Seq	Field Name	HL7 v2 Data Type	Opt / Rep	HL7 Table & Operational Usage Notes
`PID-1`	Set ID – PID	`SI` (Sequence ID)	O / N	1-based sequence integer (`1`, `2`, …) when multiple `PID` segments appear in a message
`PID-2`	Patient ID (External)	`CX`	B / N	Deprecated / Backward Compatibility Only (v2.4+): Replaced by repeating `PID-3`
`PID-3`	Patient Identifier List	`CX` (Extended Composite ID)	R / Y	Required & Repeating (`~`): Carries MRN (`MR`), EMPI (`PI`), SSN, Driver’s License (`DL`), and Clinical Trial Subject ID (`RI`) per HL7 Table 0203
`PID-4`	Alternate Patient ID	`CX`	B / Y	Deprecated (v2.4+): Consolidated into `PID-3` repetitions
`PID-5`	Patient Name	`XPN` (Extended Person Name)	R / Y	Required & Repeating: `Family^Given^Middle^Suffix^Prefix^Degree^NameTypeCode` (Table 0200: `L` Legal, `A` Alias, `M` Maiden, `B` Birth)
`PID-6`	Mother’s Maiden Name	`XPN`	O / Y	Used as a secondary biometric/demographic discriminator in EMPI probabilistic matching
`PID-7`	Date/Time of Birth	`DTM` (or `TS`)	O / N	Format `YYYYMMDD` or `YYYYMMDDHHMMSS` (time of birth critical for neonatal ICU & twin matching)
`PID-8`	Administrative Sex	`IS`	O / N	HL7 Table 0001: `F` (Female), `M` (Male), `O` (Other), `U` (Unknown), `A` (Ambiguous), `N` (Not applicable)
`PID-10`	Race	`CWE` (or `CE`)	O / Y	Repeating coded element using CDC Race and Ethnicity Code Set (CDCREC, HL7 Table 0005, e.g., `2106-3` White, `2054-5` Black or African American)
`PID-11`	Patient Address	`XAD` (Extended Address)	O / Y	`Street1^Street2^City^State^Zip^Country^AddressType` (Table 0190: `H` Home, `M` Mailing, `B` Business, `C` Current/Temporary)
`PID-13`	Phone Number – Home	`XTN` (Extended Telecom)	O / Y	Repeating telecom structure carrying telephone, mobile (`CP`), and email (`NET^Internet`)
`PID-18`	Patient Account Number	`CX`	O / N	Visit-specific or episode-specific billing account / HAR number (distinct from lifetime MRN in `PID-3`)
`PID-19`	SSN Number – Patient	`ST`	B / N	Deprecated for security/HIPAA reasons: Modern interfaces omit SSN or pass via `PID-3` with type `SS` only when required by law
`PID-22`	Ethnic Group	`CWE` (or `CE`)	O / Y	HL7 Table 0189 / OMB CDCREC codes (`2135-2` Hispanic or Latino, `2186-5` Not Hispanic or Latino)
`PID-24 / 25`	Multiple Birth Indicator & Order	`ID` / `NM`	O / N	`PID-24` (`Y`/`N` Table 0136) and `PID-25` (`1`, `2`, …) prevent newborn twin/triplet EMPI collisions when `PID-5` (`BABYBOY`) and `PID-7` match
`PID-29 / 30`	Patient Death Date/Time & Indicator	`DTM` / `ID`	O / N	`PID-29` records timestamp of death; `PID-30` (`Y`/`N`) flags deceased status

Composite Data Types Inside `PID-3` (`CX`) and `PID-5` (`XPN`) with Annotated Example

Why did HL7 v2.4+ deprecate `PID-2`, `PID-4`, and `PID-19` in favor of a single repeating field (`PID-3`)? Because a patient in an integrated health system simultaneously possesses a hospital Medical Record Number (`MR`), an Enterprise Master Patient Index UUID (`PI`), a health plan Member ID (`MA`/`MC`), and—if enrolled in a clinical study—a Clinical Trial Subject ID (`RI`). By using the tilde (`~`) repetition delimiter inside `PID-3` with the `CX` (Extended Composite ID with Check Digit) data type, a single field unambiguously tags the assigning authority and identifier type of every ID:

`CX.1` (ID Number): The identifier string (e.g., `MRN884120`).
`CX.4` (Assigning Authority — `HD`): Subcomponents `NamespaceID&UniversalID(OID)&UniversalIDType(ISO)` identifying which hospital or trial issued the ID.
`CX.5` (Identifier Type Code — HL7 Table 0203): `MR` (Medical Record Number), `PI` (Patient Internal Identifier), `PT` (Patient External Identifier), `AN` (Account Number), `RI` (Generalized Resource / Research Subject Identifier), `DL` (Driver’s License), `SS` (Social Security Number).

Annotated HL7 v2.5.1 `PID` Segment Example

PID|1||MRN884120^^^METRO_HOSP&2.16.840.1.113883.3.999&ISO^MR~SUBJ-0419^^^NCT05512345&2.16.840.1.113883.3.888&ISO^RI||GARCIA^ELENA^SOFIA^^DR^^L~MARTINEZ^ELENA^^^^^M|LOPEZ|198104150830|F||2106-3^White^CDCREC|450 BROOKLINE AVE^APT 4B^BOSTON^MA^02215^USA^H||^PRN^PH^^^617^5550199~^NET^Internet^[email protected]|||||ACT99201442||||2135-2^Hispanic or Latino^CDCREC||N||||||N

`PID-3`: Two tilde-separated (`~`) identifiers: (1) Hospital MRN `MRN884120` assigned by `METRO_HOSP` (`CX.5 = MR`), and (2) Clinical Trial Subject ID `SUBJ-0419` assigned by protocol `NCT05512345` (`CX.5 = RI`).
`PID-5`: Two tilde-separated (`~`) `XPN` names: Legal name (`XPN.7 = L`) `Dr. Elena Sofia Garcia` and Maiden name (`XPN.7 = M`) `Elena Martinez`.
`PID-6`: Mother’s maiden surname `LOPEZ`.
`PID-7` & `PID-8`: Born `1981-04-15` at `08:30` (`198104150830`), Administrative Sex `F`.
`PID-10` & `PID-22`: OMB/CDC Race (`2106-3` White) and Ethnic Group (`2135-2` Hispanic or Latino).
`PID-13`: Repeating `XTN` containing primary residence phone (`(617) 555-0199`) and email address (`NET^Internet`).

HL7 v2 `PID` Segment to HL7 FHIR R4 `Patient` Resource Mapping

When an integration engine or clinical data repository converts HL7 v2 feeds into HL7 FHIR resources, the HL7 v2-to-FHIR Implementation Guide maps `PID` fields to the FHIR R4 `Patient` resource (and `Account` resource for `PID-18`) as follows:

HL7 v2 `PID` Field	HL7 FHIR R4 `Patient` Element	Transformation & ValueSet Translation Rules
`PID-3` (`CX[]`)	`Patient.identifier[]` (`Identifier`)	`CX.1` $to$ `value`; `CX.4.2` OID $to$ `system` (`urn:oid:…`); `CX.5` $to$ `type.coding` (`http://terminology.hl7.org/CodeSystem/v2-0203`)
`PID-5` (`XPN[]`)	`Patient.name[]` (`HumanName`)	`XPN.1` $to$ `family`; `[XPN.2, XPN.3]` $to$ `given[]`; `XPN.4` $to$ `suffix[]`; `XPN.5` $to$ `prefix[]`; `XPN.7` (`L`/`A`/`M`) $to$ `use` (`official`/`nickname`/`maiden`)
`PID-6` (`XPN`)	Extension `patient-mothersMaidenName`	`XPN.1.1` mapped to `valueString` on `http://hl7.org/fhir/StructureDefinition/patient-mothersMaidenName`
`PID-7` (`DTM`)	`Patient.birthDate` (`date`)	Reformats `YYYYMMDD` to ISO-8601 `YYYY-MM-DD`; if `HHMMSS` present, attaches `patient-birthTime` (`valueDateTime`) extension
`PID-8` (`IS`)	`Patient.gender` (`code`)	Maps Table 0001 `M` $to$ `male`, `F` $to$ `female`, `O`/`A` $to$ `other`, `U`/`N` $to$ `unknown`
`PID-10 / 22` (`CWE`)	US Core `us-core-race` & `us-core-ethnicity`	Maps CDCREC codes into `ombCategory` and `detailed` sub-extensions required by ONC USCDI
`PID-11` (`XAD[]`)	`Patient.address[]` (`Address`)	`XAD.1`/`2` $to$ `line[]`; `XAD.3` $to$ `city`; `XAD.4` $to$ `state`; `XAD.5` $to$ `postalCode`; `XAD.6` $to$ `country`
`PID-13 / 14` (`XTN[]`)	`Patient.telecom[]` (`ContactPoint`)	Maps `XTN.3` (`PH`/`CP`/`FX`/`Internet`) to `system` (`phone`/`fax`/`email`) and `XTN.2` (`PRN`/`WPN`) to `use` (`home`/`work`/`mobile`)
`PID-24 / 25`	`Patient.multipleBirth[x]`	If `PID-25` integer present $to$ `multipleBirthInteger`; else `PID-24` (`Y`/`N`) $to$ `multipleBirthBoolean`
`PID-29 / 30`	`Patient.deceased[x]`	If `PID-29` timestamp present $to$ `deceasedDateTime`; else `PID-30` (`Y`/`N`) $to$ `deceasedBoolean`

HIPAA Safe Harbor De-Identification (45 CFR § 164.514(b)) and Clinical Trial `PID` Scrubbing

In clinical research data warehousing and secondary real-world data (RWD) pipelines, the `PID` segment is the primary locus of Protected Health Information (PHI). Of the 18 HIPAA Safe Harbor identifiers defined in 45 CFR § 164.514(b)(2), the majority map directly to `PID` fields: Names (`PID-5`, `PID-6`), Geographic subdivisions smaller than a state (`PID-11.1–11.3`, and `PID-11.5` ZIP code beyond the first 3 digits), Month and Day of Birth or Age > 89 (`PID-7`), Death Date month/day (`PID-29`), Telephone/Fax/Email (`PID-13`, `PID-14`), SSN (`PID-19` / `PID-3` `SS`), Medical Record Numbers (`PID-3` `MR`), and Account Numbers (`PID-18`).

Before routing HL7 v2 `ORU^R01` laboratory messages from a hospital interface engine to a clinical trial Electronic Data Capture (EDC) system or central biobank, outbound interface filters execute an automated `PID` pseudonymization transform: stripping `PID-5`, `PID-6`, `PID-11`, `PID-13`, `PID-18`, and `PID-19`, truncating `PID-7` to birth year (`YYYY`), and retaining only the study-specific Research Subject Identifier repetition (`PID-3` where `CX.5 = RI`) matched via the site’s protected linkage table.

Frequently Asked Questions

What is the HL7 PID segment?

The HL7 `PID` (Patient Identification) segment is the primary demographic and identity segment in HL7 Version 2 (`v2.x`) clinical messages (including `ADT`, `ORM`, `ORU`, `SIU`, `DFT`, and `VXU`). Defined in Chapter 3 of the HL7 v2 standard, the `PID` segment carries the patient’s repeating identifier list in `PID-3` (Medical Record Number, Enterprise Master Patient Index ID, and Research Subject ID using the `CX` data type), legal and alias names in `PID-5` (`XPN`), date/time of birth in `PID-7` (`DTM`), administrative sex in `PID-8`, race and ethnicity in `PID-10` and `PID-22`, address in `PID-11` (`XAD`), telecom in `PID-13`/`PID-14` (`XTN`), and billing account number in `PID-18`.