Health Level 7 – Basics to Latest

What is HL7?

HL7 is a standard concerned with the exchange of messages between two or more computers in the health care organization.  It is also concerned with the interoperability within the healthcare enterprise related to exchange, integration, sharing and retrieval of electronic health information.

The name “Health Level-7” is a reference to the seventh “application” layer of the ISO OSI Reference model. The name indicates that HL7 focuses on application layer protocols for the health care domain, independent of lower layers. HL7 effectively considers all lower layers merely as tools.

The term “Level 7” refers to the highest implementation protocol level for a definition of a networking framework as presented in the Open System Interconnection (OSI) model of the International Organization for Standardization (ISO). HL7 does, however, correspond to the conceptual definition of an application-to-application interface placed in the seventh layer of the OSI model. In the OSI conceptual model, the functions of both communications software and hardware are separated into seven layers, or levels. The HL7 Standard is primarily focused on the issues that occur within the seventh, or application, level. These are the definitions of the data to be exchanged, the timing of the exchanges, and the communication of certain application-specific errors between the applications.

The seventh level supports functions such as security checks, participant identification, availability checks, exchange mechanism negotiations and, most importantly, data exchange structuring.

HL7 Organization:

HL7 organization is an international community of healthcare subject matter experts and information scientists collaborating to create standards for the exchange, management and integration of electronic healthcare information. HL7 promotes the use of such standards within and among healthcare organizations to increase the effectiveness and efficiency of healthcare delivery for the benefit of all.

HL7 develops Conceptual Standards (i.e. HL7 RIM), Document Standards (i.e. HL7 CDA), Application Standards (i.e. HL7 CCOW) and Messaging Standards (i.e. HL7 v2.x and v3.0). Messaging standards are particularly important because they define how information is packaged and communicated from one party to another. Such standards set the language, structure and data types required for seamless integration from one system to another

HL7 however does not specify how messages will be delivered between the applications and other network protocols such as TCP/IP or FTP file transfers will be used to deliver messages.Equally HL7 does not describe what is done to a message after it has been received as this is the domain of the individual applications.

HL7 Versions:

There have been a few versions of HL7 but the most recent of them all is the version 3.0.The HL7 version 2 standard has the aim to support hospital workflows. It was originally created in 1987. The HL7 version 3 standard has the aim to support any and all healthcare workflows. Development of version 3 started around 1995, resulting in an initial standard publication in 2005. The v3 standard, as opposed to version 2, is based on a formal methodology (the HDF) and object oriented principles.

The HL7 Version 3 Standard currently addresses the interfaces among various healthcare IT systems that send or receive patient admissions/registration, discharge or transfer (ADT) data, queries, resource and patient scheduling, orders, results, clinical observations, billing, master file update information, medical records, scheduling, patient referral, patient care, clinical laboratory automation, application management and personnel management messages.

Need for a standard:

The organization and delivery of healthcare services is an information intensive effort. It is generally accepted that the efficacy of healthcare operations is greatly affected by the extent of automation of information management functions.

In the past four decades, healthcare institutions, and hospitals in particular, have begun to automate aspects of their information management. Initially, such efforts were focused towards reducing paper processing, improving cash flow, and improving management decision making. In later years a distinct focus on streamlining and improving clinical and ancillary services has evolved, including bedside (in hospitals and other inpatient environments) and “patient-side” systems (in ambulatory settings).

Today, growing numbers of hospitals have installed computer systems to manage a wide range of their information needs – admission, discharge and transfer; clinical laboratories; radiology; billing and accounts receivable, to cite a few. Often these applications used for specific areas have been developed by different vendors or, occasionally, by in-house groups, with each product having highly specific information format. As hospitals have gradually expanded information management operations, a parallel need to share critical data among the systems has emerged.

Comprehensive systems that aim at performing most, if not all, healthcare information management are in production by many vendors. These systems may be designed in a centralized or a distributed architecture. Nevertheless, to the extent that such systems could be and are implemented as truly complete, their use would lessen the need for an external data interchange standard such as HL7. Network technology has emerged as a viable and cost-effective approach to the integration of functionally and technically diverse computer applications in healthcare environments. However, these applications have developed due to market structure rather than through a logical systems approach; they are therefore often ad hoc and idiosyncratic. At the very least, they do not possess common data architecture; their combined data storage actually constitutes a highly distributed and severely de-normalized database and the processes that they support can vary significantly. Extensive site-specific programming and program maintenance are often necessary for interfacing these applications in a network environment.

The need for extensive site-specific interface work could be greatly reduced if a standard for network interfaces for healthcare environments were available and accepted by vendors and users alike. Finally, the lack of data (or inconsistent data) and process standards between both vendor systems and the many healthcare provider organizations presents a significant barrier to application interfaces. It is proposed that HL7 can act as a superstructure in this environment to facilitate a common specification and specifications methodology. It is indeed both practical and economical to develop, and commit to, standard interfaces for computer applications in healthcare institutions.

Goals of the Standards

HL7’s purpose is to facilitate communication in healthcare settings.The following are some of the goals which HL7 is expected to achieve in the healthcare environment.

a) The primary goal is to provide standards for the exchange of data among healthcare computer applications that eliminate or substantially reduce the custom interface programming and program maintenance that may otherwise be required

b)  Immediate transfer of single transactions should be supported along with file transfers of multiple transactions.

c) The Standard must support evolutionary growth as new requirements are recognized. This includes support of the process of introducing extensions and new releases into existing operational environments

Hence HL7 is the most important standard for information technology to succeed in the healthcare environment and to increase the efficiency of the healthcare delivery process.

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