Summary
This whitepaper contains 2 use case descriptions. Each use case could be supported by either the HL7 v2.x or the HL7 v3 messaging standard. Each example use case has two example messages associated with it: a HL7 v2.x message, and its functional equivalent in v3. The whitepaper aims to show some the differences as well as similarities between example v2.x and v3 message instances.
1. Introduction
This whitepaper has the aim to illustrate how v2 message strcutures are present in v3, and vice versa. As you're probably aware of, HL7 v3 is not backwards compatible with the v2.x standard although some of the message constructs (e.g. data types) are similar in nature. Nevertheless, all use cases supported by v2.x are supported by v3. Not that it is not the intent of this whitepaper to discuss migration issues from v2.x to v3, nor to discuss the circumstances where using v3 may be more appropriate than v2.x as a messaging standard. It merely attempts to show some of the similarities between v2.x and v3 using message examples.
2. Laboratory Results use case
This section contains an example business use case related to a laboratory results message, as well as a V2.4 and a v3 representation. The v3 message is based upon the normative XML ITS 1.0 and schema from the May 2006 Informative Edition of HL7 v3. The use case is the completion of a serum glucose laboratory result of 182 mg/dL authored by Howard H. Hippocrates. The laboratory test was ordered by Patricia Primary for patient Eve E. Everywoman. The use case takes place in the US Realm.
2.1 The V2.4 Message
The V2.4 representation of the use-case is a ORU^R01 message. The syntax encoding is based on the classic HL7 v2 syntax, commonly referred to as the vertical-bar syntax. The MSH (Message Header) segment contains the message type, in this case, ORU^R01, which identifies the message type and the trigger event. The sender is the GHH Lab in ELAB-3. The receiving application is the GHH OE system located in BLDG4. The message was sent on 2002-02-15 at 09:30. The MSH segment is the initial segment of the message structure.
MSH|^~\&|GHH LAB|ELAB-3|GHH OE|BLDG4|200202150930||ORU^R01|CNTRL-3456|P|2.4 PID|||555-44-4444||EVERYWOMAN^EVE^E^^^^L|JONES|19620320|F|||153 FERNWOOD DR.^ ^STATESVILLE^OH^35292||(206)3345232|(206)752-121||||AC555444444||67-A4335^OH^20030520 OBR|1|845439^GHH OE|1045813^GHH LAB|15545^GLUCOSE|||200202150730||||||||| 555-55-5555^PRIMARY^PATRICIA P^^^^MD^^|||||||||F||||||444-44-4444^HIPPOCRATES^HOWARD H^^^^MD OBX|1|SN|1554-5^GLUCOSE^POST 12H CFST:MCNC:PT:SER/PLAS:QN||^182|mg/dl|70_105|H|||F
The PID (Patient Identification) segment contains the demographic information of the patient. Eve E. Everywoman was born on 1962-03-20 and lives in Statesville OH. Her patient ID number (presumably assigned to her by the Good Health Hospital) is 555-44-4444.
The OBR (Observation Request) segment identifies the observation as it was orignally ordered: 15545^GLUCOSE. The observation was ordered by Particia Primary MD and performed by Howard Hippocrates MD.
The OBX (Observation) segment contains the results of the observation: 182 mg/dl.
2.2 The v3 Message
The v3 representation of the use case is a POLB_IN224200 interaction. The root element of the XML instance contains information necessary for its proper validation. The root element is POLB_IN224200. The XML ITS version 1.0 uses a single v3 namespace for all instances. All IDs use OIDs as the method of ensuring global uniqueness. The following object identifiers (OIDs, not present in the HL7 V2 message) are used within the Good Health Hospital (GHH):
- GHH Application IDs: 2.16.840.1.113883.19.1122.1
- GHH Lab Interaction IDs: 2.16.840.1.113883.19.1122.7
- GHH Location IDs: 2.16.840.1.113883.19.1122.2
- GHH Provider (Person) IDs: 2.16.840.1.113883.19.1122.3
- GHH Patient IDs: 2.16.840.1.113883.19.1122.5
- GHH Placer Order IDs: 2.16.840.1.113883.19.1122.14
- GHH Lab Filler Order IDs: 2.16.840.1.113883.19.1122.4
- The code system for the observation within the GHH is LOINC: 2.16.840.1.113883.6.1
- USA Social Security Number (SSN): 2.16.840.1.113883.4.1
- The HL7 Interactions Type code system: 2.16.840.1.113883.1.6
- The HL7 Trigger Event code system: 2.16.840.1.113883.1.8
- The HL7 ConfidentialityCode code system: 2.16.840.1.113883.5.25
2.2.1 The v3 Message - Transmission Wrapper
Note that the root element uniquely identifies the message’s interaction identifier, in this case, POLB_IN224200, which identifies the message type, the trigger event, and the receiver responsibilities. The receiving application is described in the receiver/device element, the sender/device element and sender/asLocatedEntity/location identify the sending application and facility. The receiver is the GHH_OE system in Bldg4. The sender is GHH_LAB at location E-LAB3. The root element wraps the payload, which is the Control Act wrapper for this message.
2.2.2 The v3 Message - Trigger Event Control Act wrapper
The message control act is yet another wrapper around the actual message. It represents the trigger event POLB_TE224200. Information about the date and time the trigger event occurred, as well as the responsible parties for the trigger event is not present in this example, even though it could be conveyed as part of the wrapper. Note that the date and time of the laboratory observation as well as the author of the observation are contained in the Domain Content and not in the Control Act wrapper.
2.2.3 The v3 Message - Domain Content
The "Domain Content" starts with its own root element – observationEvent. The elements within specify the type of observation, the ID, the time of the observation, statusCode, and the results. The value for the actual result is shown in the value element. The interpretationCode element shows that the value has been interpreted as high (H), while referenceRange provides the normal values for this particular observation.
The performing provider, Mr. Harold H Hippocrates, is included with his ID and name. There are two levels of information present, the practitioner level and the person level. The ID is on the practitioner level, while the name is on the person level.
Harold
H
Hippocrates
MD
The patient, Eve E. Everywoman, is also represented with two levels - the patient and the person. The available elements within the patient element are few since this is part of a closely-coupled message (e.g. the address isn’t sent). On the other hand, the id is available as well as the name, thus providing for at least some form of error checking.
Eve
E
Everywoman
The original order for the laboratory observation is referenced by the FLFS act relationship named inFulfillmentOf, which identifies the order by placer number. This number should be used by the receiver to match the results to the order. The available elements within the placerOrder element are few since this is part of a closely-coupled message (e.g. the details of the ordering provider aren’t sent).