Chapter 6: EHR Integration & Data Standards

"Without interoperability there can be no real CDSS. Standards-based data exchange makes seamless information flow between healthcare systems possible."

6.1 The HL7 FHIR Standard

FHIR (Fast Healthcare Interoperability Resources) is the HL7 standard for modern healthcare data exchange. WIA-MED-015 requires HL7 FHIR R4 or later.

🎯 Core FHIR Concepts

📋 Key FHIR Resources

// Patient resource example (JSON)
{
  "resourceType": "Patient",
  "id": "example",
  "name": [{
    "family": "Kim",
    "given": ["Min-su"]
  }],
  "gender": "male",
  "birthDate": "1985-03-15",
  "address": [{
    "city": "Seoul",
    "postalCode": "06234"
  }]
}

// Observation resource (blood pressure)
{
  "resourceType": "Observation",
  "status": "final",
  "category": [{
    "coding": [{
      "system": "http://terminology.hl7.org/CodeSystem/observation-category",
      "code": "vital-signs"
    }]
  }],
  "code": {
    "coding": [{
      "system": "http://loinc.org",
      "code": "85354-9",
      "display": "Blood pressure panel"
    }]
  },
  "subject": {"reference": "Patient/example"},
  "effectiveDateTime": "2025-01-15T09:30:00Z",
  "component": [
    {
      "code": {"coding": [{"system": "http://loinc.org", "code": "8480-6", "display": "Systolic blood pressure"}]},
      "valueQuantity": {"value": 140, "unit": "mmHg", "system": "http://unitsofmeasure.org", "code": "mm[Hg]"}
    },
    {
      "code": {"coding": [{"system": "http://loinc.org", "code": "8462-4", "display": "Diastolic blood pressure"}]},
      "valueQuantity": {"value": 90, "unit": "mmHg", "system": "http://unitsofmeasure.org", "code": "mm[Hg]"}
    }
  ]
}

🔗 FHIR API Operations

# Read a patient
GET /Patient/12345

# The patient's most recent blood-pressure observations
GET /Observation?patient=12345&code=85354-9&_sort=-date&_count=10

# The patient's active medications
GET /MedicationStatement?patient=12345&status=active

# Create a new prescription
POST /MedicationRequest
{
  "resourceType": "MedicationRequest",
  "status": "active",
  "intent": "order",
  "subject": {"reference": "Patient/12345"},
  "medicationCodeableConcept": {
    "coding": [{
      "system": "http://www.nlm.nih.gov/research/umls/rxnorm",
      "code": "314076",
      "display": "lisinopril 10 MG Oral Tablet"
    }]
  },
  "dosageInstruction": [{
    "text": "Take 10 mg once daily"
  }]
}

6.2 Medical Terminology Standards

Standardized terminologies are essential for consistent exchange of medical data.

📚 Major Terminologies

🌐 Korean Standards

• KCD (Korean Standard Classification of Diseases) — based on ICD-10
• EDI codes — national health-insurance claims
• ATC codes — drug classification (WHO)
• Korean standard drug codes — managed by the Korea Pharmaceutical Information Service (KPIS) at HIRA; product approvals by MFDS

6.3 The CDS Hooks Standard

CDS Hooks is the HL7 standard for integrating a CDSS into the EHR workflow. WIA-MED-015 requires CDS Hooks 2.0 or later.

⚡ CDS Hooks Flow

1. An event occurs in the EHR
   ↓
2. A hook fires (e.g., "order-sign")
   ↓
3. EHR → CDS service request
   {
     "hook": "order-sign",
     "hookInstance": "d1577c69-dfbe-44ad-ba6d-3e05e953b2ea",
     "context": {
       "userId": "Practitioner/example",
       "patientId": "12345",
       "draftOrders": { ... }
     }
   }
   ↓
4. The CDS service performs its analysis
   - DDI check
   - Allergy check
   - Dose verification
   ↓
5. CDS service → EHR response (Cards)
   {
     "cards": [
       {
         "summary": "⚠️ Warfarin-Aspirin interaction",
         "indicator": "warning",
         "detail": "Increased bleeding risk...",
         "source": {"label": "WIA-MED-015 DDI service"},
         "suggestions": [
           {"label": "Review antiplatelet choice"}
         ]
       }
     ]
   }
   ↓
6. The EHR displays the cards in the UI
   ↓
7. The physician decides (accept / choose alternative / override)

🔧 Main Hook Types

6.4 Data Quality Management

✅ Dimensions of Data Quality

🔍 Data Validation Example

// Blood-pressure data validation
{
  "systolic": 140,
  "diastolic": 90
}

Validation rules:
✅ Completeness: systolic AND diastolic present
✅ Range: 50 < systolic < 300
✅ Range: 30 < diastolic < 200
✅ Logic: systolic > diastolic
⚠️ Warning: systolic >= 130 (above the < 130/80 target)

// Medication data validation
{
  "medication": "Lisinopril",
  "dose": "10",
  "unit": "mg",
  "route": "PO"
}

Validation:
✅ RxNorm code matched
✅ Dose range (2.5-80 mg/day)
✅ Valid route of administration
✅ Frequency format

6.5 Privacy and Security

🔒 Regulatory Compliance

🛡️ Security Technologies

• Encryption — in transit: TLS 1.3; at rest: AES-256
• Access control — RBAC, ABAC, OAuth 2.0 (SMART on FHIR scopes)
• Audit logs — every access recorded
• De-identification — identifiers removed for analytics
• Backup and recovery — disaster-recovery plan

Chapter Summary

弘益人間 · Benefit All Humanity

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