Elixir HL7 View Source

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An Elixir library for working with HL7 v2.x healthcare data

Elixir HL7 provides functions to parse, query and modify healthcare data that conforms to the HL7 v2.x standards. It should be able to reconstruct any HL7 Message without data loss or corruption.

It also provides basic support for reading HL7 file streams with configurable delimiters (MLLP included).

This library has been tested on a fairly wide variety of real-world HL7 messages to ensure correctness and flexibility.

You can learn more about HL7 here:

Please report an issue if something appears to be handled incorrectly.

Getting started

Full documentation can be found at hex.pm.

Add this library to your mix.exs file:

defp deps do
  [{:elixir_hl7, "~> 0.6.4"}]

Check out the HL7.Examples module for sample data that you can use to explore the API.


HL7 messages can be minimally validated to gather header (MSH segment) information for quick routing and acknowledgements.

iex> hl7_text = HL7.Examples.wikipedia_sample_hl7()
...> raw_msg = HL7.Message.raw(hl7_text)
...> raw_msg.header.message_type

See the HL7.RawMessage and HL7.Header modules for more information.


HL7 messages can be fully parsed into lists of lists and strings to provide a compact representation of the message structure.

One could grab the 2nd segment in a message:

iex> HL7.Examples.wikipedia_sample_hl7()
...> |> HL7.Message.to_list()
...> |> Enum.at(1)
["EVN", "", "200605290901", "", "", "", "200605290900"]

Or get the field value of RXA-5.2 (finding the first RXA segment's 5th field, 1st repetition, 2nd component):

iex> HL7.Examples.nist_immunization_hl7()
...> |> HL7.Message.find("RXA")
...> |> HL7.Segment.get_part(5, 1, 2)

It's also possible to modify the data within a segment (but it is much easier to manipulate messages using the HL7.Query module):

iex> HL7.Examples.wikipedia_sample_hl7()
...> |> HL7.Message.find("EVN")
...> |> HL7.Segment.replace_part("extra data", 5, 2, 1)
  ["", "", ["", "extra data"]],

See the HL7.Message and HL7.Segment modules for more information.


Advanced manipulation and analysis of HL7 messages can be performed with the HL7.Query module.

It supports a pipeline-friendly API modeled after jQuery and D3, allowing set-based document operations and queries.

Messages can be broken into groups using a segment selector (similar to a CSS selector string) that denotes optional and repeating segments in potentially nested hierarchies.

Individual segments can be decomposed using a field selector to reference specific field, repetition, component and subcomponent indices.

Note that all HL7.Query selections implicitly retain the entire message structure such that elements can be selected, modified and then used to reconstruct a new HL7 message.

The act of selecting something never modifies the content of a message. Applying other methods to a selection, such as delete, filter, append, etc., does modify the actual message content.

For instance, this would select all textual diagnoses (DG1-3.2) associated with a patient visit (PV1):

iex> import HL7.Query
iex> HL7.Examples.nist_syndromic_hl7()
...> |> select("PV1 [{DG1}]")
...> |> select("DG1")
...> |> get_parts("3.2")
["Cryptosporidiosis", "Dehydration", "Diarrhea"]

The statement select("PV1 [{DG1}]") grabs a list of segment groups containing a PV1 segment and any DG1 segments that might follow it. Thus, we would select one group containing a PV1 segment and three DG1 segments.

  [ # 1 group of 4 segments
    ["PV1", "1", "(data truncated to fit)"],
    ["DG1", "1", "", [["0074", "Cryptosporidiosis", "I9CDX"]], "", "", "F"],
    ["DG1", "2", "", [["27651", "Dehydration", "I9CDX"]], "", "", "F"],
    ["DG1", "3", "", [["78791", "Diarrhea", "I9CDX"]], "", "", "F"]

Then select("DG1") creates three groups of individual DG1 segments by searching within the confines of the prior selection.

[  # 3 groups of 1 segment each
  [["DG1", "1", "", [["0074", "Cryptosporidiosis", "I9CDX"]], "", "", "F"]],
  [["DG1", "2", "", [["27651", "Dehydration", "I9CDX"]], "", "", "F"]],
  [["DG1", "3", "", [["78791", "Diarrhea", "I9CDX"]], "", "", "F"]]

Finally, get_parts("3.2") will return a flattened list of data containing the 3rd field, 1st repetition (the default), 2nd component for each selected segment.

["Cryptosporidiosis", "Dehydration", "Diarrhea"]

Alternately, one could select and remove every diagnosis tied to a patient visit and then output a modified HL7 message:

iex> import HL7.Query
iex> HL7.Examples.nist_syndromic_hl7()
...> |> select("PV1 [{DG1}]")
...> |> select("DG1")
...> |> delete()
...> |> to_string()
"MSH|^~\\&||LakeMichMC^9879874000^NPI|||201204020040||ADT^A03^ADT_A03|NIST-SS-003.32|P|2.5.1|||||||||PH_SS-NoAck^SS Sender^2.16.840.1.114222.4.10.3^ISO\rEVN||201204020030|||||LakeMichMC^9879874000^NPI\rPID|1||33333^^^^MR||^^^^^^~^^^^^^S|||F||2106-3^^CDCREC|^^^^53217^^^^55089|||||||||||2186-5^^CDCREC\rPV1|1||||||||||||||||||33333_001^^^^VN|||||||||||||||||09||||||||201204012130\rOBX|1|CWE|SS003^^PHINQUESTION||261QE0002X^Emergency Care^NUCC||||||F\rOBX|2|NM|21612-7^^LN||45|a^^UCUM|||||F\rOBX|3|CWE|8661-1^^LN||^^^^^^^^Diarrhea, stomach pain, dehydration||||||F\r"  

The following query extracts each Common Order (ORC) group's OBX segments and outputs a list of each order's associated vaccine types.

iex> import HL7.Query
iex> HL7.Examples.nist_immunization_hl7()
...> |> select("ORC [RXA] [RXR] {OBX}")
...> |> filter(fn q -> get_part(q, "3.2") == "vaccine type" end)
...> |> map(fn q -> get_parts(q, "5.2") end)
    ["Influenza, unspecified formulation"], 
    ["DTaP", "Polio", "Hep B, unspecified formulation"]

See the HL7.Query module for more information.


HL7 messages can be constructed from scratch with the HL7.Message module. Passing an HL7.Header struct to HL7.Message.new/1 will produce a base message upon which you can add additional segments. These can be appended as list data.

The final raw message can be produced by invoking the to_string/1 protocol on either the HL7.Query or HL7.Message structs.


The HL7 module contains utility functions to open file streams of HL7 message content with support for MLLP and standard :line storage. Other formats are somewhat supported by specifying expected prefix and suffix delimiters between messages.


A separate library, Elixir-MLLP, exists to manage MLLP connections. MLLP is a simple protocol on top of TCP that is commonly used for sending and receiving HL7 messages.


This project is approaching a v1.0 release. The API is mostly stable at this point.

Also, please be aware of the details of the license (Apache 2.0).


  1. Planning to add a loose selector like OBX* to basically split on a segment type, to create groups beginning a specific segment name.
  2. Working to release a complementary MLLP library
  3. Building a sister library to handle FHIR messages


Elixir-HL7 source code is released under Apache 2 License. Check the LICENSE file for more information.