Bangladesh Core FHIR Implementation Guide - Published by Ministry of Health and Family Welfare. See the Directory of published versions

ICD-11 Implementation

Overview

The Bangladesh Core FHIR Implementation Guide uses ICD-11 Mortality and Morbidity Statistics (MMS) as the mandatory coding system for clinical conditions. This page documents the system URI, terminology infrastructure, conformance requirements, and postcoordination conventions for implementers.

System URI

All ICD-11 MMS codes SHALL use the WHO canonical system URI:

http://id.who.int/icd/release/11/mms

The preferred code form is the short stem code (e.g. 1A00, NC72.Z). Linearization URIs are not used as code identifiers in this IG.

Terminology Infrastructure

National OCL Terminology Server

Runtime code validation and lookup are delegated to the national OpenConceptLab (OCL) terminology server operated by DGHS/MoHFW:

Public FHIR R4 endpoint: https://tr.ocl.dghs.gov.bd/api/fhir

OCL hosts ICD-11 MMS version 2025-01 with 26,284 concepts in the following concept classes: Diagnosis (13,389), Finding (5,119) and Substance (7,776).

Vendors do not interact with OCL directly. All vendor submissions are validated at the HIE boundary via the Bangladesh ICD-11 Cluster Validator (see Cluster Expressions below).

Supported OCL Operations

The following FHIR terminology operations are supported. CodeSystem $validate-code takes the code system as url=; CodeSystem $lookup takes it as system=. Using system= with $validate-code returns false.

CodeSystem $validate-code

GET https://tr.ocl.dghs.gov.bd/api/fhir/CodeSystem/$validate-code
    ?url=http://id.who.int/icd/release/11/mms&code={code}

CodeSystem $lookup

GET https://tr.ocl.dghs.gov.bd/api/fhir/CodeSystem/$lookup
    ?system=http://id.who.int/icd/release/11/mms&code={code}

ValueSet $validate-code

GET https://tr.ocl.dghs.gov.bd/api/fhir/ValueSet/$validate-code
    ?url=https://fhir.dghs.gov.bd/core/ValueSet/bd-condition-icd11-diagnosis-valueset
    &system=http://id.who.int/icd/release/11/mms&code={code}

Unsupported OCL Operations

$expand is not supported — this is a known limitation of the national OCL instance. The ICD-11 ValueSets in this IG are therefore declared as stubs over a CodeSystem with content not-present, so the IG contains no expansion. Implementers SHALL NOT depend on $expand for ICD-11 ValueSets in this IG.

ICD-11 Docker Instance

A WHO ICD-11 Docker instance is maintained by DGHS at https://icd11.dghs.gov.bd running release 2025-01, and is publicly available. It serves as the import source for OCL and as the backend for the cluster validator.

Condition.code Binding and Class Restriction

Condition.code is bound to the Bangladesh ICD-11 MMS Condition ValueSet at required strength. This ValueSet includes only Diagnosis (13,389) and Finding (5,119) class concepts — 18,508 concepts total as of version 2025-01.

Condition.code SHALL contain at least one coding conforming to the coding[stem] slice with system = http://id.who.int/icd/release/11/mms. Vendors cannot omit ICD-11 by substituting a local code.

The following concept classes SHALL NOT appear as standalone stem codes in Condition.code: Substance, Organism, Device, Anatomy, Misc.

This restriction exists because these classes represent entities that are not themselves diagnoses or clinical findings — they are axes used in postcoordination (e.g. a causative substance, an affected anatomy site). Their correct use is as satellite codes within a cluster expression, not as standalone condition codes.

Class restriction is enforced at runtime via OCL ValueSet $validate-code against the Bangladesh ICD-11 MMS Condition ValueSet. At the HAPI FHIR layer, enforcement is via RemoteTerminologyServiceValidationSupport configured to call OCL, which is deployed.

The coding[stem] slice is open (#open) — additional local codings are permitted alongside the mandatory ICD-11 stem.

Cluster Expressions

Background

ICD-11 supports postcoordination — the combination of a stem code with one or more satellite codes to precisely represent a clinical concept that cannot be expressed by a stem code alone. A postcoordinated expression is called a cluster expression.

Cluster expressions are typically sourced from the WHO Electronic Coding Tool (ECT) at the point of care.

Syntax

A cluster expression combines a stem code with satellite codes using the & operator (combination) or / operator (specificity):

NC72.Z&XK8G&XJ7ZH&XJ7YM

Where:

• NC72.Z — stem code: Fracture of femur, unspecified
• XK8G — satellite: laterality
• XJ7ZH — satellite: fracture subtype
• XJ7YM — satellite: fracture open or closed

FHIR Representation

The stem code is carried in Coding.code. The full cluster expression is carried in the ICD-11 Cluster Expression extension on the same Coding element:

"code": {
  "coding": [
    {
      "system": "http://id.who.int/icd/release/11/mms",
      "code": "NC72.Z",
      "display": "Fracture of femur, unspecified",
      "extension": [
        {
          "url": "https://fhir.dghs.gov.bd/core/StructureDefinition/icd11-cluster-expression",
          "valueString": "NC72.Z&XK8G&XJ7ZH&XJ7YM"
        }
      ]
    }
  ],
  "text": "Fracture of femur, unspecified — left, transverse, closed"
}

The stem code in Coding.code SHALL match the leading stem code in the cluster expression string.

Stem-Only vs Cluster

The cluster validator explicitly rejects stem-only expressions. Single stem codes SHALL be represented in Coding.code only and validated via OCL $validate-code.

Satellite Code Class Restriction Exemption

Satellite codes in a cluster expression are exempt from the Diagnosis/Finding class restriction that applies to stem codes in Condition.code. Substance, Anatomy, Organism, and other axis codes are valid and expected as satellites.

Bangladesh ICD-11 Cluster Validator

All postcoordinated cluster expressions SHALL be validated against the Bangladesh ICD-11 Cluster Validator prior to submission to the HIE:

POST https://icd11.dghs.gov.bd/cluster/validate
Content-Type: application/json

{"expression": "NC72.Z&XK8G&XJ7ZH&XJ7YM"}

Example response:

{
  "valid": true,
  "stem": {
    "code": "NC72.Z",
    "display": "Fracture of femur, unspecified",
    "ocl_validated": true
  },
  "satellites": [
    {"code": "XK8G",  "axis": "laterality",           "valid": true},
    {"code": "XJ7ZH", "axis": "fractureSubtype",       "valid": true},
    {"code": "XJ7YM", "axis": "fractureOpenOrClosed",  "valid": true}
  ],
  "errors": []
}

The cluster validator is a mandatory HIE boundary gate. All vendor submissions containing postcoordinated ICD-11 expressions pass through it.

Conformance Statements

ICD-11-CONF-01: ICD-11 MMS codes SHALL use system URI http://id.who.int/icd/release/11/mms. Stem code validation is available via OCL at: https://tr.ocl.dghs.gov.bd/api/fhir/CodeSystem/$validate-code?url=http://id.who.int/icd/release/11/mms&code={code}

ICD-11-CONF-02: The icd11-cluster-expression extension SHALL only be present when the expression contains at least one postcoordination satellite code using & or / operators. Single stem codes SHALL be represented in Coding.code only and validated via OCL $validate-code.

ICD-11-CONF-03: Postcoordinated cluster expressions SHALL be validated against the Bangladesh ICD-11 Cluster Validator at https://icd11.dghs.gov.bd/cluster/validate prior to submission to the HIE.

ICD-11-CONF-04: Condition.code SHALL contain at least one coding conforming to the coding[stem] slice with system = http://id.who.int/icd/release/11/mms. The stem code SHALL be a member of the Bangladesh ICD-11 MMS Condition ValueSet, which includes only Diagnosis and Finding class concepts. This restriction is enforced at runtime via OCL ValueSet $validate-code.

ICD-11-CONF-05: Substance, Organism, Device, Anatomy, and Misc class ICD-11 concepts SHALL NOT appear as standalone stem codes in Condition.code. This restriction does not apply to satellite codes carried in the icd11-cluster-expression extension.