Coding

A code from a standardized medical terminology system, equivalent to FHIR's Coding datatype. Contains a code value, the system it belongs to, and display text. Supports SNOMED-CT, LOINC, ICD-10/11, ATC, RxNorm, CPT, and other international and national coding systems.

Overview

Coding represents a single concept from a medical terminology or classification system. It is the fundamental building block for encoding clinical concepts in a standardized, interoperable way. Each Coding includes the code value, the terminology system that defines it, an optional version, and human-readable display text. This entity aligns with the FHIR Coding datatype for healthcare interoperability.

Key Concepts

Coding Structure

Each Coding contains:

Terminology Systems

Clinical Terminologies

• SNOMED-CT - Comprehensive clinical terminology for diagnoses, procedures, findings
• LOINC - Laboratory and clinical observation identifiers
• ICD-10 / ICD-11 - International disease classification for diagnoses
• CIM-10-FR - French adaptation of ICD-10

Medication Terminologies

• ATC - Anatomical Therapeutic Chemical classification (WHO)
• RxNorm - US drug terminology with ingredients, strengths, forms
• NDC - National Drug Code (US product identifiers)

Procedure Terminologies

• CPT - Current Procedural Terminology (US procedures/services)
• CCAM - Classification Commune des Actes Médicaux (French procedures)
• NABM - Nomenclature des Actes de Biologie Médicale (French lab acts)
• NGAP - Nomenclature Générale des Actes Professionnels (French professional acts)

Vaccine Terminologies

• CVX - CDC vaccine administered codes

Version Importance

The version field is critical because:

• Code meanings can change between versions
• New codes are added, some deprecated
• Hierarchies and relationships evolve
• Regulatory requirements may specify versions

User Selection Flag

The userSelected boolean indicates:

• true - A clinician explicitly chose this code
• false - System inferred, defaulted, or auto-populated
• Important for clinical decision support and quality reporting

Calculated System URL

The systemUrl field computes the canonical FHIR URI:

Use Cases

Diagnosis Coding

When recording a diagnosis:

1. Search terminology by display text or code
2. Select appropriate code from results
3. Set userSelected: true for clinician-chosen codes
4. Include version for temporal consistency
5. Store in diagnosis record

Laboratory Order Coding

When ordering lab tests:

1. Use LOINC codes for test identification
2. Map to local lab system codes if needed
3. Include display text for result reports
4. Version ensures consistent interpretation

Medication Coding

When prescribing medications:

1. Use RxNorm for US systems, ATC for international
2. Encode ingredient, strength, and form
3. Map to NDC for dispensing
4. Cross-reference for drug interactions

Procedure Coding

For billing and documentation:

1. Use CPT (US) or CCAM (France) for procedures
2. Include modifier codes as needed
3. Validate against payer requirements
4. Document in encounter record

FHIR Interoperability

When exchanging data:

1. Use canonical system URIs
2. Include version when available
3. Provide display text for human readers
4. Validate codes against terminology servers

Related Entities

Calculated Fields

Enums

system