At a very high level, both the CCR and HL7 are used for moving clinical data. The CCR happens to be using XML tags and HL7 2.X uses an “old school” format known as “encoding rules seven” (ER7). I often call HL7’s format “pipe-and-hat” for its use of vertical bars (|) and caret (^) characters.
The most interesting difference between the two standards is the context in which the standards are used. As noted previously, the CCR was designed to move data between facilities while HL7 grew up moving data within the four walls of hospitals. Thus, the CCR is focused on inter-facility communication while HL7 is focused on the intra-facility messaging.
HL7 2.X is a “triggered” and real time protocol. That is, systems within the hospital want to know where a patient is right now. They want to receive lab results within seconds of them being entered. The pharmacy system needs notification when new prescriptions are written. And so on.
Contrast that with a document like a patient referral or discharge summary. Such a document is a summation of many real time events — a history of illness, a list of current medications, prior lab results, etc. There is little “real time” about a document that summarized prior data.
Clearly you could build a history of a patient’s record by listening to a non-stop stream of HL7 messages. But you would need to piece them all together to make a summary. For example, there would be no single HL7 2.X message that contains all current medications the patient is taking. Instead, there would be a stream of pharmacy orders that each indicate a new or updated prescription.
In summary, the difference between the standards boils down to the facts that HL7 is focused on intra-facilty, real time data movement — what is happening now? — while the CCR is focused on inter-facilty, “summarized” data movement — what happened before now?
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