CodeableConcept and Coding in FHIR: how one concept carries several codes

Short answer: In FHIR, a Coding is one code from one code system: a system (the URL of the code system), a code and a human display. A CodeableConcept is the concept as a whole: a list of Codings that mean the same thing in different systems, plus text, the words the clinician or the lab actually used. Diagnoses, tests, medicines and allergies are all CodeableConcepts.

Why several codings

A lab may send its own local code and a LOINC code for the same test; a diagnosis may carry SNOMED CT and ICD-10. Keeping all of them lets each receiving system pick the one it understands, and keeping text preserves what was written.

"code": {
  "coding": [
    {"system": "http://loinc.org", "code": "2160-0", "display": "Creatinine [Mass/volume] in Serum or Plasma"},
    {"system": "https://lab.example.org/codes", "code": "CREA"}
  ],
  "text": "Creatinine"
}

Mistakes to avoid

• A code without a system: the code is meaningless outside your database.
• Invented system URLs for standard terminologies: LOINC is http://loinc.org, SNOMED CT http://snomed.info/sct, UCUM http://unitsofmeasure.org.
• Dropping the original text when you map to a standard code.
• Treating display as the identifier: systems match on system + code.

In Anpheros

Anpheros keeps the original name from the report as text and adds the standard coding (LOINC, ATC, ICD-10, SNOMED CT) so data stays readable to people and systems. Developers: FHIR code systems and normalizing medical data.

Related pages

• What is a LOINC code? The number behind each test on your lab report
• What is SNOMED CT? Clinical terms as codes, explained simply
• UCUM units in lab results

Sources

• HL7 FHIR R4: Data types

Frequently asked questions

What is the difference between Coding and CodeableConcept?

A Coding is one code from one system; a CodeableConcept is a concept with one or more Codings and the original text.

What is the system URL for LOINC?

http://loinc.org

Should I keep local codes?

Yes, next to the standard coding. They help trace data back to the source.

Is display used to match codes?

No. Matching uses system and code; display is for people.

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Anpheros builds a medical record that the patient controls and can share with any clinic, on an HL7 FHIR R4 platform, based in the EU. These guides help you understand and organise your health; they do not replace your doctor.

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