node-hl7-v2

This is Redox's battle-tested in-house HL7v2 parser/generator.

The online HL7v2 Parser can give you a sense of what it's capable of.

Join us in public Slack channel to chat about this project:


HL7 Version 2 (HL7v2)

HL7’s Version 2.x (V2) Messaging Standard
is the most ubiquitous healthcare data exchange standard. This module converts HL7v2 messages to and from a JSON representation.

Usage

The parser/generator can be used to convert a wide range of HL7v2 messages from the delimited HL7v2 format to a schema-fied JSON version.
When messages don't match the schema, the module supports a custom schema. See Custom Schemas below for more information.

Parser

``
const rawData = MSH|^~\&|||...;
const hl7v2 = require('@redoxengine/redox-hl7-v2');
const parser = new hl7v2.Parser();
const jsonData = parser.parse(rawData);
`

Generator

`
const ackJSON = {
"MSH": {
"0": "MSH",
"1": "|",
"2": "^~\\&",
"3": {
"1": "CHERDABEE"
},
"5": {
"1": "REDOX"
},
"6": {
"1": "RDX"
},
"7": {
"1": "20150915004731"
},
"9": {
"1": "ACK",
"2": "S12"
},
"10": "20150915004731",
"11": {
"1": "T"
},
"12": {
"1": "2.3"
}
},
"MSA": {
"0": "MSA",
"1": "AA",
"2": "1"
}
};

const hl7v2 = require('@redoxengine/redox-hl7-v2');
const generator = new HL7v2.Generator();
const data = generator.write(ackJSON);
//MSH|^~\\&|CHERDABEE||REDOX|RDX|20150915004731||ACK^S12|20150915004731|T|2.3|||||||||\rMSA|AA|1||||\r
`

Understanding the HL7v2 schema


Our approach to parsing/generating HL7 is schema-driven. The Schema is based on the HL7v2 specification.
The best way to understand it is through the schema folder:
`
schema/
index.js - entry point to access the schema
dataTypes/ - contains definitions for each "Data Type" in HL7v2 (See chapter 2A)
fields/ - contains a definition for each field. Each file is named .
messages/ - contains the actual structure for each message definition, this file also contains "Groups"
segments/ - contains definitions of which fields are in a segment
structure/ - contains a map from HL7 message/event type to structure definition.
`

Basics

There are many events defined in HL7, but some share the same structure. For example ADT^A01 and ADT^A04 both have the same ADT^A01 structure.

Once the structure is identified the code looks at the corresponding schema in schema/messages. Each message definition is object where the properties are "Segment Groups". The Group with the same name as the message type is the root. So in ORU_R01.json, the ORU_R01 property has exactly 1 required MSH segment, unlimited SFT segments, and a PATIENT_RESULT group.
`
{
...
"ORU_R01": {
"elements": [
{
"minOccurs": "1",
"maxOccurs": "1",
"segment": "MSH"
},
{
"minOccurs": "0",
"maxOccurs": "unbounded",
"segment": "SFT"
},
{
"minOccurs": "1",
"maxOccurs": "unbounded",
"group": "PATIENT_RESULT"
},
{
"minOccurs": "0",
"maxOccurs": "1",
"segment": "DSC"
}
]
}
}
``

Overriding the schema

Existing HL7v2 implementations don't often respect rules about segment groups and segment order, so custom schemas can be used at will. Pass a JSON object to the constructor of either the parser or the generator to use a custom Schema. It will get merged with the existing schema.

Examples of custom schemas can be found here:
* Adding a Z-segment

HL7 Trademark and IP Statement

HL7® and HEALTH LEVEL SEVEN® are trademarks owned by Health Level Seven International. HL7® and HEALTH LEVEL SEVEN® are registered with the United States Patent and Trademark Office.