The HL7.Examples module contains functions with sample data that you can use in unit tests or to explore the API,

iex> hl7_text = HL7.Examples.wikipedia_sample_hl7()
...> to_string()
...> Enum.take(30)
"ADT" copy

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
"ADT" copy

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"]copy

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)
"Influenza"copy

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)
[      
  "EVN",
  "",
  "200605290901",
  "",
  "",
  ["", "", ["", "extra data"]],
  "200605290900"
]copy

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")
...> |> find_all(~p"3.2")
["Cryptosporidiosis", "Dehydration", "Diarrhea"]copy

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"]
  ]
]copy

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"]]
]copy

Finally, find_all(~p"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"]copy

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"  copy

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 -> find_first(q, ~p"3.2") == "vaccine type" end)
...> |> map(fn q -> find_all(q, ~p"5.2") end)
[
    ["Influenza, unspecified formulation"], 
    ["DTaP", "Polio", "Hep B, unspecified formulation"]
]   copy

See the HL7.Query module for more information.

Create

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.