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Interoperability Toolkit 2 Messaging API standards

API standards for a set of messaging components using HL7 V2 and HL7 V3.


These API standards cover a set of messaging specifications known as the Interoperability Toolkit (ITK). Primarily consisting of ITK Release 2 (ITK2), they also include earlier versions.

They're used, for example, for sending messages about the admission, discharge and transfer (ADT) of a patient.

They are based on HL7 V2 and HL7 V3 standards. For example, ITK2.2 includes specific messaging domains based on HL7 V2, and also a number of message domains based on HL7 V3 - most notably the CDA messaging specifications which are used by NHS 111 domain messaging.

For more details on this API standard, see the Interoperability Toolkit Core download below.

These API standards were later supplemented by the Interoperability Toolkit 3 (ITK3) Messaging Distribution FHIR API standards to support newer specifications, for example Transfer of Care, which is not supported under ITK2.

For further information, contact the ITK conformance team.


These API standards are in draft.

API standards

Click to download a zip file and extract all the files into a folder on your local PC. 
Select the index file to view the API standard.

Last edited: 14 September 2023 5:45 pm