Healthcare data standards map: HL7, DICOM, IHE, SNOMED, LOINC, ICD

1. Two classification axes — exchange and semantics

When people first encounter healthcare data standards, they often assume they need to pick a single standard. In reality, the standards map is drawn on two complementary, not competing, axes. The first axis defines how data is packaged and transmitted between two systems. The second defines what the values inside that data actually mean. Understanding these two axes is the prerequisite for reading RFPs correctly, evaluating bids fairly, and avoiding pointless arguments like "FHIR replaces SNOMED CT."

Some standards do not fit neatly onto these two axes. CDA and FHIR Composition belong to the document architecture family — conventions for how multiple data fragments combine into a clinical document. The RIM in HL7 v3 and the openEHR reference model belong to the reference model family — abstract scaffolding for every clinical entity, from which detailed archetypes are derived. IHE is not itself a new standard but rather a set of integration profiles that bind HL7, DICOM, and OAuth into runnable scenarios.

2. Summary table of 10 core standards

The table below is the heart of this page. The Vietnam status column reflects the situation as of May 2026 and will be updated as new regulations appear. The Legal references column lists only domestic ministry decisions; for international standards without a Vietnamese counterpart, the cell is left blank.

3. Exchange standards — HL7, DICOM, IHE

HL7 v2, v3, CDA, and FHIR

HL7 is the oldest family of standards in digital health. HL7 v2 dates back to 1988, with V2.0 in September 1988, V2.1 in March 1990, and V2.3 in March 1997. It uses pipe-delimited syntax and remains the backbone of HIS-LIS-RIS integration. HL7 v3 with the RIM was more ambitious but also more complex, gaining little adoption outside CDA. HL7 FHIR launched as DSTU1 on September 30, 2014. The current R4 release (4.0.1) ships 146 resources blending Normative and STU material, and is the modern standard recommended for any new project. For a deeper dive into the HL7 family and how FHIR differs from v2, see What is HL7 and What is FHIR.

DICOM

DICOM stands for Digital Imaging and Communications in Medicine, stewarded by NEMA in the United States. It comprises three tightly coupled parts: the .dcm file format that embeds metadata alongside pixels, the DIMSE network protocol for sending and querying studies, and clinical workflows such as Modality Worklist, Modality Performed Procedure Step, and Structured Report. Every modality from X-ray, CT, MRI, and ultrasound to PET emits DICOM. In Vietnam, DICOM is the de facto standard across PACS systems, applied through vendor compliance without any dedicated regulation. Detail page: DICOM in Vietnamese healthcare.

IHE profiles

IHE — Integrating the Healthcare Enterprise — is not a new standard but a collection of integration profiles. Each profile specifies actors, transactions, and concrete choices drawn from HL7, DICOM, and OAuth to solve a single use case, for example sharing documents across organizations. Well-known profiles include XDS (Cross-Enterprise Document Sharing), PIX (Patient Identifier Cross-reference), and MHD (Mobile access to Health Documents). Vietnam does not yet have an official IHE-Vietnam Affiliate, but XDS and MHD patterns appear implicitly in some HIE projects. Detail page: IHE profiles.

4. Reference model — openEHR

openEHR is not an exchange standard; it belongs to the reference model family. Its approach cleanly separates two layers: an abstract, stable Reference Model at the bottom, and clinician-defined archetypes and templates on top that describe specific concepts such as blood pressure, prescriptions, and lab results. This split gives openEHR strong clinical depth and suits long-lived medical record systems.

From a practical standpoint, openEHR and FHIR do not collide head-on. openEHR typically serves as the internal core EHR with rich clinical modeling, while FHIR sits on the outside as the API layer for external exchange. Several countries — the UK, Australia, Brazil, and the Nordics — operate both side by side. In Vietnam, openEHR has effectively no production footprint; the community will need to revisit it if a large-scale electronic medical record project requires deep information modeling. Detailed comparison at openEHR vs FHIR.

5. Semantic standards — SNOMED, LOINC, ICD, RxNorm, UCUM

SNOMED CT

SNOMED CT is the world's largest clinical terminology, with roughly 350,000 multi-hierarchical concepts, governed by SNOMED International. The organization requires national-level members to pay a membership fee to use and distribute it internally. Vietnam has begun localization in three batches: batch 1 for Body Structure under Decision 2427/QĐ-BYT (25/07/2025), batch 2 for Morphologic Abnormality under Decision 2493/QĐ-BYT (2025), and batch 3 for Allergy and Finding under Decision 2805/QĐ-BYT (04/09/2025). It is the richest semantic resource but also the most complex, requiring careful binding strategies in the VN Core IG. Detail page: SNOMED CT in Vietnam.

LOINC

LOINC — Logical Observation Identifiers Names and Codes — is maintained by the Regenstrief Institute and codes clinical observations and laboratory tests. The code set is free and is the default choice for Observation.code in FHIR. Vietnam has only a partial mapping so far, via Decision 1227/QĐ-BYT (11/04/2025) — the shared diagnostic test catalog batch 1 covering 2,964 indicators across hematology, biochemistry, microbiology, anatomical pathology, and diagnostic imaging. Each indicator can be mapped to a corresponding LOINC code in subsequent batches. Detail page: LOINC in Vietnam.

ICD-10 and ICD-11

ICD-10 is the tenth revision of the International Classification of Diseases issued by the WHO, and remains Vietnam's official disease classification standard. The localized version was issued under Decision 4469/QĐ-BYT (28/10/2020), with COVID-19 codes (U07.1, U07.2) added under Decision 98/QĐ-BYT (14/01/2022). ICD-11 took global effect on 01/01/2022; the WHO encourages national transitions but allows ICD-10 to continue in parallel as needed and sets no hard deadline. Vietnam has no formal ICD-11 adoption roadmap yet. Detail page: ICD-10 VN.

ICD-9-CM Volume 3

ICD-9-CM Volume 3 classifies surgeries and procedures, branching off from the main ICD-10 line. Many Asian countries continue to use ICD-9-CM for DRG algorithms and for coding their technical service catalogs. Vietnam issued the 2026 edition under Decision 387/QĐ-BYT (05/02/2026), superseding the 2020 edition under Decision 4440/QĐ-BYT (now obsolete). The new edition serves as the basis for Procedure coding in VN Core and as input for social health insurance (BHYT) reimbursement.

RxNorm and ATC

RxNorm is maintained by the U.S. National Library of Medicine and is the drug terminology of the U.S. market. ATC — Anatomical Therapeutic Chemical — is governed by the WHO Collaborating Centre for Drug Statistics and classifies medications by organ of action and therapeutic group. Vietnam has not adopted RxNorm; ATC, by contrast, appears in the Vietnamese Pharmacopoeia and in Ministry of Health drug catalog circulars and is widely used for utilization analytics and procurement. When encoding Medication.code in FHIR, Vietnamese projects typically combine an internal drug code with the corresponding ATC code.

UCUM

UCUM — Unified Code for Units of Measure — is maintained by the Regenstrief Institute and provides a formal grammar for unit codes. In FHIR R4, the Quantity data type encodes units through two fields: Quantity.system points to http://unitsofmeasure.org and Quantity.code carries the corresponding UCUM code. The Quantity.unit field is a human-readable display string only and plays no part in comparison or conversion logic. This is a common implementation pitfall: many systems populate Quantity.unit but leave code empty, which destroys cross-system computability.

6. How the standards fit together

The two axes of healthcare data standards do not run independently. A single clinical event — say, returning a lipid panel result — invokes several standards at once, layered on top of each other. A FHIR Resource plays the role of the exchange envelope. The code field inside binds to the appropriate terminology. Units of measure use UCUM. When the data becomes a document, it is wrapped in a FHIR Composition or a CDA. For cross-organization exchange, an IHE profile sets the context and security. When imaging is involved, DICOM holds the original image while FHIR carries only metadata references.

[Clinical event]
  └── packaged as a FHIR Resource (exchange)
        ├── code field bound to SNOMED CT / LOINC / ICD (semantics)
        ├── Quantity unit uses UCUM
        ├── transported over REST + OAuth 2.0 (security)
        ├── if a document → CDA or FHIR Composition + Bundle
        ├── if imaging → DICOM Study + FHIR ImagingStudy reference
        └── if cross-enterprise → IHE XDS or MHD profile

Take a lipid panel result as an illustration. A FHIR Observation acts as the envelope. The code field binds to LOINC 2093-3 for total cholesterol. The valueQuantity field carries the value 5.2 with system = http://unitsofmeasure.org and code = mmol/L per UCUM. The subject field references a Patient identified by the national ID card (CCCD). If the result is wrapped into a discharge document, a Composition bundles the Observations, Conditions, and MedicationRequests, is digitally signed under Decree 137/2024/NĐ-CP, and is then transmitted via the IHE MHD profile. The same clinical event ends up touching five or six standards together — and that is perfectly normal.

7. Adoption status in Vietnam

The picture of healthcare data standards adoption in Vietnam through mid-2026 falls into three clearly distinct buckets: standardized, in progress, and not yet present.

Standardized and mandatory

• ICD-10 VN under Decision 4469/QĐ-BYT (28/10/2020), with COVID codes added under Decision 98/QĐ-BYT (14/01/2022) — mandatory for social health insurance (BHYT) reporting and medical records.
• ICD-9-CM Volume 3 (2026 edition) under Decision 387/QĐ-BYT (05/02/2026), superseding Decision 4440/QĐ-BYT (2020) — used for procedure coding and DRGs.
• DICOM across nearly all PACS systems — a de facto standard enforced through vendor contracts.

In progress

• SNOMED CT VN — three batches under Decisions 2427/QĐ-BYT, 2493/QĐ-BYT, and 2805/QĐ-BYT (2025) — to be expanded across more hierarchy branches.
• Partial LOINC mapping via the diagnostic test catalog batch 1 under Decision 1227/QĐ-BYT (11/04/2025) — 2,964 indicators that need to be mapped to LOINC codes in subsequent batches.
• HL7 FHIR — a community-led VN Core IG draft is under development, not yet codified into law.
• HL7 v2 — used ad hoc in many private hospitals for HIS-LIS integration, with no nationally standardized version.

No formal deployment yet

• IHE profiles — no IHE-Vietnam Affiliate; XDS and MHD patterns appear only implicitly.
• openEHR archetypes — no large-scale production project.
• RxNorm — no adoption roadmap; ATC is the international drug code in widespread use.
• ICD-11 — globally effective since 2022, but Vietnam has no national roadmap yet.

8. Recommended stack for new EMR projects

Circular 13/2025/TT-BYT (06/06/2025) sets the deadline for non-hospital healthcare facilities to deploy electronic medical records (EMR) by 31/12/2026 at the latest. If you are building an EMR from scratch, the following reference stack reduces both legal and integration risk.

Minimum stack

• Exchange: FHIR R4 (4.0.1) for every new API; HL7 v2 only as a bridge to existing HIS-LIS legacy systems.
• Diseases and diagnoses: ICD-10 VN for Condition.code, per Decisions 4469/QĐ-BYT and 98/QĐ-BYT.
• Surgeries and procedures: ICD-9-CM 2026 for Procedure.code, per Decision 387/QĐ-BYT.
• Lab tests and diagnostic indicators: LOINC plus the diagnostic test catalog under Decision 1227/QĐ-BYT for Observation.code; partial LOINC mapping first, expanded in later batches.
• Rich clinical terminology: SNOMED CT VN for the localized branches (Body Structure, Morphologic Abnormality, Allergy, Finding) per Decisions 2427, 2493, and 2805.
• Imaging: DICOM for the original files; FHIR ImagingStudy holds reference metadata.
• Units of measure: UCUM for Quantity.system and Quantity.code.
• Clinical documents: FHIR Composition and Bundle document for discharge summaries, referrals, and prescriptions.

Extended stack

• VN Core IG profiling: inherit the official profiles at the canonical http://fhir.hl7.org.vn/core/ to ensure interoperability with the community ecosystem.
• SMART on FHIR: for mobile and third-party applications needing safe access.
• FHIR Bulk Data API ($export): for population analytics and AI pipelines — must be reconciled with Law 91/2025/QH15 and Decree 356/2025/NĐ-CP on personal data.
• IHE patterns: MHD and XDS when cross-facility interconnection over an HIE is required.

9. Frequently asked questions

Which standards require a license fee?

SNOMED CT requires Vietnam to join SNOMED International as a national member and pay membership fees. HL7 (including v2, v3, and FHIR) is free for any use. LOINC is free. DICOM is free. ICD-10 and ICD-11 are issued by the WHO at no cost; localized editions are issued by the Ministry of Health. ICD-9-CM Volume 3 is free. UCUM is free.

Will ICD-11 replace ICD-10?

ICD-11 took global effect on 01/01/2022. The WHO encourages national transitions but allows ICD-10 to continue in parallel as needed and sets no hard deadline. Vietnam has no formal ICD-11 adoption roadmap as of May 2026; all BHYT reporting, medical records, and health statistics still use ICD-10 VN per Decision 4469/QĐ-BYT.

openEHR vs FHIR — which one should I pick?

The two standards do not sit on the same axis. FHIR is an exchange standard with 146 resources and a REST API; openEHR is a reference model plus archetypes for the core EHR. In Vietnam's context, FHIR R4 is the priority choice given the national roadmap, the VN Core ecosystem, and BHYT interoperability requirements. openEHR is a better fit for in-house medical record projects that need detailed and long-lived clinical modeling, and can be combined with FHIR at the outermost API layer.

Do I still need FHIR if I have DICOM?

DICOM and FHIR complement each other rather than competing. Image pixels and technical metadata still live inside DICOM Studies; FHIR ImagingStudy only carries the reference and clinical context metadata. PACS is not displaced by a FHIR rollout; on the contrary, FHIR helps anchor images into a richer clinical context.

Is IHE actually needed in Vietnam?

IHE profiles become necessary when multiple healthcare facilities and services interconnect over an HIE. As long as integration is contained within a single hospital or corporate group, plain FHIR is usually enough. When scaling out across multiple facilities, profiles such as XDS, PIX, and MHD become useful blueprints.

10. References

Vietnamese legal documents

• Decision 4469/QĐ-BYT (28/10/2020) — ICD-10 VN. Referenced in the legal corpus.
• Decision 98/QĐ-BYT (14/01/2022) — adds COVID-19 codes (U07.1, U07.2) to ICD-10 VN. See QD-98-2022.
• Decision 1227/QĐ-BYT (11/04/2025) — diagnostic test code catalog batch 1 (2,964 indicators). See QD-1227-2025.
• Decision 2427/QĐ-BYT (25/07/2025) — SNOMED CT VN batch 1 (Body Structure). See QD-2427-2025.
• Decision 2493/QĐ-BYT (2025) — SNOMED CT VN batch 2 (Morphologic Abnormality). See QD-2493-2025.
• Decision 2805/QĐ-BYT (04/09/2025) — SNOMED CT VN batch 3 (Allergy + Finding). See QD-2805-2025.
• Decision 387/QĐ-BYT (05/02/2026) — ICD-9-CM Volume 3, 2026 edition. See QD-387-2026.
• Circular 13/2025/TT-BYT (06/06/2025) — electronic medical records, effective 21/07/2025.

International technical documents

• HL7 FHIR R4 (4.0.1) specification — hl7.org/fhir/R4.
• FHIR Quantity datatype — hl7.org/fhir/R4/datatypes.html#Quantity.
• SNOMED International value proposition — snomed.org/value-proposition.
• LOINC getting started — loinc.org/get-started/getting-loinc.
• WHO ICD-11 implementation FAQ — who.int (ICD-11 FAQ).
• DICOM Standard 2024 — dicomstandard.org/current.
• IHE profile catalog — ihe.net/resources/profiles.
• openEHR Architecture Overview — specifications.openehr.org.

11. Further reading