Health Level 7 Standard

Just as people should speak one language to understand each other, computer applications should interact through the general protocol to communicate. In 1987 development of HL7 protocol for safe data exchange between medical applications began. Over time HL7 gained wide circulation and universal recognition as the most often used standard of compatibility (interoperability) in the world.

Health Level 7, or HL7, represents a set of the international standards developed by Health Level Seven International, the world developer organization of standards in interconnection area of medical information systems. These standards define how electronic information is transferred between medical applications – in other words as there is an exchange, integration and extraction of data^[1].

HL7 standards can be separated into the following categories:

• Primary standards (Primary Standards) are the most often used standards relating to integration of systems, compatibility and compliance
• Fundamental standards (Foundational Standards) defining the main tools and blocks for creation of standards and also technology infrastructure which should adhere
• Clinical and administrative domains (Clinical and Administrative Domains) containing standards of messages and documentation for clinical specialties and groups
• EHR Profiles is the function models and profiles providing management of electronic medical records
• Implementation Guides, including auxiliary documents and other additional materials
• Rules and links (Rules and References), i.e. technical specifications, program structures and guide to software development and standards
• Education and awareness (Education & Awareness) – useful resources and tools for increase in understanding and application of HL7 standards

HL7 in practice

According to HL7 standards, medical data go in the form of the message containing one record or one element of information. Records about a status of patients, laboratory records, payment information and similar medical and administrative data are common examples of such messages.

HL7 messages can be transferred, for example, from rural hospital where the number of doctors is small, to big city hospital where it is much more resources. Information on health of the patient – indicators of pressure, pulse and body temperature – goes to a remote database. Having analyzed the received data, the experienced doctor from city hospital makes the diagnosis and registers proper treatment.

Actually, HL7 protocol can be used in many medical projects where the compatibility of medical devices is required. Besides, it can be applied to extraction of statistical information from the database of a number of hospitals. However HL7 protocol not only facilitates work of physicians – it allows patients to exercise digital control of the treatment.

HL7 version 3. Basic information model

HL7 version 3. Architecture of clinical documents (CDA)

• Level 1: only metadata (heading).
• Level 2: Level 1 + structure of the document (section).
• Level 3: Level 2 + the medical terms (coded for machining).

Local expansions of standards

• Z-segment (HL7 v.2.x). Non-standard elements can be used only when detailed studying of the standard shows that they have no other alternative.
• Informal expansions (HL7 v.3 CDA). Expansions should not change sense of standard elements and non-standard elements should be capable to ignore annexes adopting them safely
• Expansions (HL7 FHIR). At all expansions used in resources the formal description available to application developers https://www.hl7.org/fhir/extensibility.html should be published

Notes