FHIR Mapping Guide

This guide explains how to exchange PublicSchema disability and functioning data over FHIR R4. It covers the two common shapes (Observation for processed results, QuestionnaireResponse for raw survey captures), the LOINC coding system, and where PublicSchema stops and implementer choice begins.

Scope: the Washington Group functioning properties (WG-SS, WG-ES, WG/UNICEF CFM) and the anthropometric and pregnancy properties that SP programs commonly receive from health-side systems. Other PublicSchema properties map to FHIR using the same general patterns documented here.

Why FHIR matters for social protection

Disability and functional-status data often originates in health systems: clinic intake, health facility registries, census disability modules that health ministries administer. When that data flows into social protection programs (cash transfer eligibility, disability allowance screening, referral pathways), the wire format is frequently FHIR.

PublicSchema does not prescribe FHIR. It documents the mapping so implementers building FHIR ingress or egress for SP systems can align their code to LOINC-coded observations without inventing their own representation.

The two patterns

Pattern 1: Observation (processed result)

Use this when you hold a single functioning result for a person, regardless of how it was captured. It is the right shape for records sitting in an SP beneficiary registry, an IPS-style summary, or a clinical system's problem/status list.

Shape:

{
  "resourceType": "Observation",
  "status": "final",
  "category": [{
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/observation-category",
      "code": "functional-status"
    }]
  }],
  "code": {
    "coding": [{
      "system": "http://loinc.org",
      "code": "<LOINC item code>",
      "display": "<LOINC display>"
    }]
  },
  "subject": { "reference": "Patient/<id>" },
  "effectiveDateTime": "<ISO 8601>",
  "valueCodeableConcept": {
    "coding": [{
      "system": "http://loinc.org",
      "code": "<LOINC answer code>"
    }],
    "text": "<label, e.g. A lot of difficulty>"
  }
}

Observation.code carries the LOINC code for the WG item. valueCodeableConcept carries the graded response from the relevant LOINC answer list (for WG severity: no_difficulty, some_difficulty, a_lot_of_difficulty, cannot_do).

Observation.category = functional-status tells consumers this is a functioning observation, not a lab or vital sign. Some jurisdictions use social-history instead; both are valid in FHIR R4.

Pattern 2: QuestionnaireResponse (raw survey capture)

Use this when you have the full form as it was administered: all items in the panel, item order preserved, skip logic traces intact. This is the right shape for census disability modules, MICS/DHS imports, and any case where you need an auditable record of the questionnaire instrument.

Shape:

{
  "resourceType": "QuestionnaireResponse",
  "status": "completed",
  "questionnaire": "http://loinc.org/q/90151-4",
  "subject": { "reference": "Patient/<id>" },
  "authored": "<ISO 8601>",
  "item": [
    {
      "linkId": "<LOINC item code>",
      "answer": [{
        "valueCoding": {
          "system": "http://loinc.org",
          "code": "<LOINC answer code>"
        }
      }]
    }
  ]
}

QuestionnaireResponse.questionnaire points at the LOINC panel URL (WG-SS panel: 90151-4). Each item.linkId is the LOINC code for a WG question. LOINC publishes WG-SS as a FHIR Questionnaire via its terminology server; consumers generally do not redefine the Questionnaire locally.

Choosing between them

You have	Use
A final "yes, they have difficulty walking" fact recorded once	Observation
The full filled-in WG-SS panel as administered	QuestionnaireResponse
Both (rare but valid)	Both, linked via Observation.derivedFrom

SP systems ingesting WG-SS from a survey typically receive QuestionnaireResponse and derive per-item Observation resources downstream when eligibility rules need the individual answers.

LOINC codes

WG-SS panel

The WG-SS panel groups the six core items (seeing, hearing, walking/climbing steps, cognition/remembering, self-care, communication). LOINC publishes this panel under code 90151-4 and makes it available as a FHIR Questionnaire at http://loinc.org/q/90151-4.

Item-level codes

LOINC assigns individual codes to each WG-SS, WG-ES, and CFM question. This guide does not enumerate them: LOINC's release schedule and the Washington Group's item additions both move faster than PublicSchema's publication cadence. Consumers needing the current codes should:

1. Pull them from LOINC's release CSV (free account required at loinc.org).
2. Or use LOINC's FHIR terminology server at https://fhir.loinc.org (requires the same account).
3. Or consult the WG's own LOINC crosswalk under the "Links to related resources" sections on washingtongroup-disability.com/question-sets/.

If no LOINC code exists for a given item (common for newer WG-ES and CFM items), implementers use a local CodeSystem and document the gap in their IG. Do not invent LOINC codes.

WG severity answer list

The WG four-point response scale (No difficulty / Some difficulty / A lot of difficulty / Cannot do at all) has its own LOINC answer list. PublicSchema's functional-difficulty-severity vocabulary aligns one-to-one with that scale: consumers map the LOINC answer codes to no_difficulty, some_difficulty, a_lot_of_difficulty, cannot_do.

IPS and national profiles

The HL7 International Patient Summary (IPS) does not currently define a functioning section. Countries and projects that need to carry WG data in an IPS-style document either:

• Extend the IPS Social History section with functional-status Observation resources, or
• Define a national profile with a dedicated disability section (example: the Australian AU Core IG, Swiss eCH disability extensions).

The PublicSchema functioning properties are compatible with both approaches. The mapping is driven by LOINC codes on the Observation.code, not by the IPS composition structure.

Anthropometric and other health properties

The same Observation pattern applies to:

• height, body_weight: LOINC body height / body weight codes; valueQuantity with cm / kg UCUM units.
• muac: LOINC mid-upper arm circumference code; valueQuantity in cm.
• stunting_status, wasting_status, underweight_status, acute_malnutrition_status: one Observation per index, with LOINC answer lists for the WHO Child Growth Standards categories.
• pregnancy_status: LOINC 82810-3 (Pregnancy status) with the LOINC LL4129-4 answer list. See schema/vocabularies/pregnancy-status.yaml for the alignment.

Related resources

• FHIR R4 Observation: http://hl7.org/fhir/R4/observation.html
• FHIR R4 QuestionnaireResponse: http://hl7.org/fhir/R4/questionnaireresponse.html
• LOINC FHIR terminology server: https://fhir.loinc.org
• WG question sets: https://www.washingtongroup-disability.com/question-sets/
• Interoperability & Mapping Guide
• Selective Disclosure