HL7 is an accredited, nationally‐recognized standard for electronic data exchange in healthcare environments. HL7 is also a set of messaging standards; the syntax for the message is designed to impose interoperability on various clinical information systems. HL7 has made it possible for laboratories to send reportable data to health departments electronically. In June 2007, HL7 released a new version of its Messaging Standard, V2.51, which supports the data elements that are required by Clinical Laboratory Improvement Act (CLIA) for the exchange of electronic laboratory information.21
The EHR lab results specification, which would allow the reporting of clinical lab results, passed ballot in December 2007, and has been incorporated into the HITSP specifications and achieved full recognition status by the Secretary in June 2008. Of note though is that the 2006 American Health Information Community (AHIC) laboratory result reporting use case provides the following functionality for laboratory results reporting and notification, and, “…is applicable to many types of laboratory tests, including but not limited to: clinical chemistry, hematology, serology, and microbiology.”22 23 The current HITSP interoperability specification (IS) 1.0 does not include the ordering of laboratory tests nor does it include resulting for all types of labs, notably anatomic pathology, complex molecular diagnostics, genetic tests and others.2425 These gaps will need to be addressed to support the more ubiquitous exchange of laboratory information.
HL7 has a balloted standard for lab order messages. This is currently supported by HL7 V2. Work is also currently underway to promote a standardized approach to lab orders. In August 2008, the AHIC released additional recommendations for General Laboratory Orders26 for public comment. The AHIC document specifies the various standards that are recommended to support the electronic ordering of laboratory tests by clinicians and the manner in which labs receive and process these orders. When the recommendations are finalized, it will be HITSP’s responsibility to work with existing standard development organizations to develop a messaging specification for lab orders. In addition to the efforts of CCHIT and HITSP, Integrating the Healthcare Enterprise (IHE),27 an organization that is focused on building detailed frameworks for the implementation of standards, has also made available a guide for the trial implementation of lab orders.28
All the labs, health centers and vendors we spoke with for this paper are using HL7 for lab messages. In many cases the HL7 interfaces were implemented before the availability of HITSP standards, and therefore do not uniformly use HL7 version 2.5.1. Even though all of the projects included in this study support the HL7 message standard, the implementations vary and the health centers or networks and labs report the need to work collaboratively to ensure
that the HL7 message segments are appropriately mapped between the sending and receiving systems. The variability in the implementation is largely due to the fact that HL7 V2.x does not use a specific information model, has vague definitions for many data fields and contains many optional fields.29
Review of the international use of HL7 indicates a growing trend to support HL7 V3 in various European countries. While there is a growing interest internationally, there are no broad scale implementations of HL7 V3 yet. Canada seems to be the furthest ahead and has developed their implementation plan for V3. There are advantages to HL7 V3, notably the use of an information model largely designed to support the interoperability of messages as well as the content of these messages. There are numerous reasons for its limited use in the United States, including: the extensive use of HL7 V2.x by legacy applications; its almost 20 years of industry experience in both private and public sectors; its enormous functionality to support different applications; and excellent vendor support.31 Another deterrent to moving from V2 to V3 is an interoperability problem between HL7 v2.x and HL7 v3 messages: there is no well‐defined mapping between HL7 v2.x and v3 messages. Additionally, HL7 V3 does not yet have a balloted standard for lab orders.