Coding Systems (1.1)

To use a new coding system with codes, the following resources must be setup:

• one or more Code Categories
• one or more Codes
• one System
• one or more System Codes

For a detailed description of all fields, please check the REST API documentation for administration and configuration.

Setup of Resource Code Category

In order to group codes and to be able to filter them more easily, code categories can be used. They have no effect on mapping.

The following example contains a code category for codes that belong to vital signs.

{
  "name": "Vital Sign",
  "code": "VITAL_SIGN",
  "description": "Vital signs.",
  "_links": {
    "self": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/codeCategories/1197b27e-3956-43dd-a75c-bfc6808dc49d"
    },
    "codeCategory": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/codeCategories/1197b27e-3956-43dd-a75c-bfc6808dc49d"
    }
  }
}

Setup of Resource Code

A code is a system independent definition of an item with the lowest required precision. E.g. for weight a measured weight or an estimated weight may exist. The code may be referenced by rules and in JavaScript without knowing the real coding system. The real coding system may be LOINC, SNOMED CT or any other coding system.

The following example contains the code for body weight in different coding systems as used by OpenMRS:

"coding": [
  {
    "system": "http://loinc.org",
    "code": "8302-2"
  },
  {
    "system": "http://snomed.info/sct",
    "code": "50373000"
  },
  {
    "system": "http://ampath.com/",
    "code": "5090"
  },
  {
    "system": "http://www.pih.org/country/malawi",
    "code": "5090"
  },
  {
    "system": "http://ciel.org",
    "code": "5090"
  },
  {
    "system": "http://www.pih.org/",
    "code": "5090"
  },
  {
    "system": "http://openmrs.org",
    "code": "5090AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
    "display": "Height (cm)"
  }
]

The following example contains a system independent definition of a code for measured bode weight:

{
  "name": "Body Weight Measured",
  "code": "BODY_WEIGHT_MEASURED",
  "mappedCode": null,
  "description": "Body weight measured",
  "enabled": true,
  "_links": {
    "self": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/codes/0d78f5e3-c9fd-4859-9768-fb7c898a4142"
    },
    "code": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/codes/0d78f5e3-c9fd-4859-9768-fb7c898a4142"
    },
    "codeCategory": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/codes/0d78f5e3-c9fd-4859-9768-fb7c898a4142/codeCategory"
    }
  }
}

The following code snippet checks if any system dependent code belongs to the system independent 'BODY_WEIGHT_MEASURED' code. This code may be used for example on a FHIR Observation Resource.

codeUtils.containsMappingCode(input.code, 'BODY_WEIGHT_MEASURED')

Setup of Coding or Identifier System

FHIR may use system dependent codes (e.g. for observations and vaccines) and system dependent identifiers (e.g. regional patient identifier). The system URI that is used for these systems is defined only once. This allows that also other information can be stored about the system and the system can also be disabled. If a system is disabled, system dependent codes are no longer mapped to system independent codes. E.g. if the system SNOMED CT is disabled and the FHIR Observation Resource does only include the SNOMED CT code for measured body weight, the FHIR Observation Resource can no longer be mapped to measured body weight and will not be processed anymore.

The following example contains the definition of the CVX coding system for vaccines. The included FHIR display name will be used when a resource is exported from DHIS 2 and resulting FHIR Resource contains the coding system.

{
  "name": "CVX (Vaccine Administered)",
  "code": "SYSTEM_CVX",
  "systemUri": "http://hl7.org/fhir/sid/cvx",
  "enabled": true,
  "description": "Available at http://www2a.cdc.gov/vaccines/iis/iisstandards/vaccines.asp?rpt=cvx. Developed by The CDC's National Center of Immunization and Respiratory Diseases (NCIRD).",
  "descriptionProtected": false,
  "fhirDisplayName": "CVX",
  "_links": {
    "self": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/systems/2601edcb-f7bc-4710-ab64-0f4edd9a2378"
    },
    "system": {
      "href": "https://demos.dhis2.org/fhir-adapter/api/systems/2601edcb-f7bc-4710-ab64-0f4edd9a2378"
    }
  }
}