Canadian Healthcare Codes and Terminology Standards

Healthcare Codes and Terminology Standards
BC Homes,
Chief Technologist
Presented in 2012
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HL7 v3 Background

Agenda
» Concepts
» Code Data Types
» Concept Domains, Code Systems and Value Sets
» Implementation Concerns

Opening Salvo
» Codes and Terminology are topics that are easy
to introduce, but tricky to understand in full complexity
» IT Professionals encounter “codes” all the time
› e-Health’s notion is really no different

Simple Examples
» The classic Canadian example
› ‘en’ or ‘fr’
» The most common example
› ‘M’ or ‘F’

Ah-ha!
» At one level, we can conclude that there’s really
nothing to this.
› We’ve all seen codes before
› What’s the big deal?

Recall one of the Complaints about
HL7 v2
» Limited rigour in use of controlled vocabularies
› Links between standard vocabularies and
message structures are ad-hoc and
implementation specific
» As a consequence, HL7v3 spells out a number
of very specific things relating to codes
› Much more rigour
› Often very exacting
› Still leaves room for Jurisdictions to make
different choices

Code Namespaces
» Consider this example:
en

Not necessarily unique
» “en” = English
» “en” = Printer’s measure
» “en” = ethylenediamine

Key Point
» Context is important
» Sometimes context might not be enough
› When we’re dealing with (for example) numeric
codes, you can have overlaps
• I don’t know of a clear case where this has
happened, but better safe than sorry

OIDs : Like Namespaces for Codes
» Conceptually, you can imagine an
implementation of codes in which all values
exist in one table
› A code is only unique when it is accompanies
with an OID
› All codes using the same OID are considered to
be part of a code system

Example
» English
› code = “en”
› codeSystem = “2.16.840.1.113883.6.84”
» XML:
<languageCode code="en" codeSystem="2.16.840.1.113883.6.84"/>
» Why does an e-Health system need a language
code?
› e.g.: no guarantee that a patient speaks any
particular language

Question
» Who decided that “en” stands for English?

Answer
» ISO : International Organization for
Standardization
» Specifically, the two-letter code for identifying
languages is part of ISO standard 639-1
› First created in 1967
› Contains 184 codes (languages)

Answer
» We can say, then, that the “meaning” of our OID,
2.16.840.1.113883.6.84, is the ISO 639-1 standard
› The “code system” is essentially means a
“published standard” (with a defined context)
› e.g: ISO 639-1 is a “published standard” to
describe “languages” (context of “language”)
» In HL7 terms, the notion of the context is called
a “Concept Domain”
› We’ll say more about this in a bit

The Treachery of OIDs
» Finding the right OID is an extremely tricky
exercise
› There are multiple places you can try to look
them up. No one source has the complete list
› And sometimes they change when you’re not
paying attention
• These are “living standards”

Looking Up OIDs

Surprise! Change!
» In the V02R02 standard, the OID for the ISO
639-1 was 2.16.840.1.113883.6.84
» In the most recently-published standard,
R02.04.02, the OID for ISO 639-1 is 1.0.639.2
› What’s more, Canada no longer uses the 2-
character language code.
• Rather than “en”, we should use “eng”
» Our important take-away: forget I ever told you
about 2.16.840.1.113883.6.84

A Moment to Discuss OIDs
» Hierarchical system
› 0: itu-t
› 1: iso
• 2: member body
› 2: joint-iso-itu-t
• 16: country
o ISO 3166 country code (e.g. Canada = 124)
2.16.124.113635

It gets more complicated
» Surely no one in this room believes that there
are only 184 languages in the world
» ISO 639-2 uses a 3-character language code
and has more than 450 entries
» ISO 639-3 also uses a 3-character language
code and has about 7700 entries
» Example:
› Arabic
• Chadian Arabic
• Libyan Arabic (and others)

How Important is this?
» Truthfully, I’m not sure
» In Canada, it might be “good enough” to record
“Arabic”, rather than “Libyan Arabic”
› But if I were implementing an e-Health system in
the middle-east, I might have a different opinion
» The important part is that the HL7 standard
recognizes that some implementations need to
make different choices

What Does this Example Reveal about the Design of HL7v3?

Key Idea
» We can talk about the notion that people have
communication preferences in a particular
“HumanLanguage” without needing to be
specific about what codes are being used
› More to the point, HL7 does define many types
this way

How is this used in HL7 Types?

XML Representation
» Here’s a portion of an HL7 message
<person classCode="PSN" determinerCode="INSTANCE" >
...
<administrativeGenderCode code="en"
codeSystem="1.0.639.1"/>
<languageCommunication>
<languageCode code="en" codeSystem="1.0.639.1"/>
</languageCommunication>
...
</person>
» Why is this wrong?

Using Concept Domains in Definitions
A portion of the message definition for PRPA_MT010001CA

Defining an HL7 Environment
» For any code attribute someone must define:
› What Concept Domain is applicable
› What Code System is bound to that Concept
Domain
» In today’s world, to the best of my knowledge,
there is no single source of all those definitions
› To the extent that much of it is defined, much of
it is defined in word documents or spreadsheets

Quick Recap
» HL7 uses codes a lot
» Codes have two parts:
› code
› code system (OID)
» A “Concept Domain” defines an abstract notion
where a code can be used
» A “Code System” is a collection of codes defined
together and managed by some group
› Formal identification via an OID (e.g. 1.0.639.1)
› Informal identification via name (e.g. ISO 639-1)

Agenda
» Concepts
» Code Data Types

Let’s Look at a Transport Wrapper

Let’s Look at a Transport Wrapper
A portion of a sample Find Candidates message

It’s Like I Totally Lied
» Where are the Code System OIDs?

Ah, But these are “Simple” Codes

Code Data Types
» CS: Coded Simple Value
» CV: Coded Value
» CE: Coded with Equivalents
» CD: Concept Descriptor
» also:
» SC: Character String with Code
» CD.LAB: Concept Descriptor (LAB)

Code Data Types
» HL7 also defines:
› CO: Coded Ordinal
» I haven’t seen this example occur in nature

Where are the Data Types defined?
» You have to consult two sources:
› The HL7 site
• http://www.hl7.org/v3ballot/html/infrastructure/
datatypes/datatypes.html
› The Data Types document of the pan-Canadian
standards releases
» The HL7 site references the international
standard; Canada has customized the standard

Example of Customization
» The International Standard for a basic Coded
Value type allows something that looks like this:
<administrativeGenderCode
code="F"
codeSystem="2.16.840.1.113883.5.1"
displayName="Female"
codeSystemName="HL7v3 AdministrativeGender" />
» The “displayName” and “codeSystemName”
properties are Not Permitted according to the
Canadian Data Types standard

Coded Simple Value (CS)
» The Code System is implicit
» This type is only used in some very limited
circumstances
› HL7 defines and manages the list of valid codes
› Usually related to
• message structure; or
• transport wrapper data.

Coded Simple in Transport Wrapper
A portion of a sample Find Candidates message

Coded Simple Value
» The Code System is implicit
» This type is only used in some very limited
circumstances
› HL7 defines and manages the list of valid codes
› Usually related to
• message structure;
• transport wrapper data; or
• part of another data type.
<quantity value="400" unit="ml" />

XML Representation
» When a CS value is “immutable” (old term:
“structural”) then the code value appears as an
XML attribute
<sender typeCode="SND" > ...
» Otherwise a CS value appears as a normal XML
element
<processingCode code="P" />
» I think it’s largely because of the first case that
they don’t show the codeSystem

Coded Value (CV)
» Possibly the most basic Code type
<administrativeGenderCode code="F"
codeSystem="2.16.840.1.113883.5.1" />

Coded with Equivalents (CE)
» Introduces the concept of “equivalent” codes
» Consider the example of HumanLanguage
<code code="eng" codeSystem="1.0.639.2">
<translation code="en" codeSystem="1.0.639.1"/>
</code>
» This is a bad example, because language code
is never defined as a “CE” type.
› Language is a pretty simple concept

Coded with Equivalents (CE)
» Consider the example of Clinical Drug
› In Canada, most pharmacists tend to refer to
drugs using DIN numbers
› Other drug numbers exist. E.g.: Health Canada
defines an Active Ingredient Group code
› There are times when they’re equivalent ways of
referring to the same thing
<code code="02147629" codeSystem="2.16.840.1.113883.5.1105">
<translation code="0131282002"
codeSystem="2.16.840.1.113883.5.1106"/>
</code>
» Both indicate 400mg of Acebutol

Concept Descriptor (CD)
» Very similar to CE
» There’s a key difference between HL7
International and HL7 Canada, here
› qualifiers
» Canada has changed its support for qualifiers
› V02R02 (MR 2007) vs. R02.04.02 (MR 2009)
» Notion of post-coordinated codes
› HL7 International would use a series of qualifiers
to provide qualifying codes

Post-Coordinated Values
» Used to combine codes more expressively
<value
code="397956004:363704007=24136001:272741003=7771000{363699004=3041200
07,260686004= 257867005}" codeSystem="2.16.840.1.113883.6.96"/>
› 397956004 = prosthetic arthroplasty of the hip
› 363704007 = Procedure site
› 24136001 = Hip joint structure
› 272741003 = laterality
› 7771000 = left
› 363699004 = direct device
› 304120007 = Total hip replacement prosthesis

Post-Coordinated Values using Qualifiers

Character String with Code (SC)
» Key idea: the string is more salient than the
code is
» Only example I know of is address parts:

Concept Descriptor for Lab (CD.LAB)
» Same as CD, but displayName is permitted

Object Hierarchy
This is a strange,
backward hierarchy

Additional Considerations
» Original Text
» Coding Strength
› CNE (coded, non-extensible)
› CWE (coded, with extensibility)

Recap
» What we’ve learned about Data Types
› CS, CV, CD, CE, SC
» Translations
» Qualifiers
» Original Text and Coding Strength

Exercise
» Find Candidates Payload
› Peruse the MIF
› Look for all the properties (attributes) that are
defined as code values
• Hint: look at <mif:type name=”??” />
› What kind of codes are they?
› Also, look at the XSDs and see how the
corresponding properties (XML Elements) are
defined there

Agenda
» Concepts
» Code Data Types

Code System and Concept Domains
» We’ve touched on Code Systems and Concept
Domains before
› All codes associated with a particular “standard”
are part of the same code system
› A Concept Domain is used to describe a
particular business concept that can be described
using a code.

Sample Concept Domains

Major Concept Domains
» ActCode
» EntityCode
» ObservationValue

Hierarchical Concept Domains

What is a Value Set?
» You could think of it as a subset of a code
system
› A value set includes some or all of the codes from
a code system
› All codes in a value set come from the same code
system

An Example
» Code System: Confidentiality
» Codes (about 14 in total)
› N: Normal
› R: Restricted
› HIV: HIV-related
› ETH: Substance-abuse related
› PSY: Psychiatry-related
› C: Celebrity
› T: Taboo

x_VeryBasicConfidentialityKind
» Only 2 codes
› N: Normal
› R: Restricted
» Note that there are relationships between codes
› Everything except “N” can been “rolled up” to “R”

Other Thoughts
» SNOMED CT
› one code system that tries to describe medical
terminology across many, many concept domains
› We generally care about specific subsets (Value
Sets), rather than the whole code system
• e.g.: ActServiceDeliveryLocationService
» Inconveniently, HL7.org often uses the same
names to describe a Value Set and a Concept
Domain
› Adds to confusion

Binding

Agenda
» Concepts
» Code Data Types

Common Healthcare Standards
» DIN
› A Drug Identification Number (DIN) is a
computer-generated eight digit number assigned
by Health Canada to a drug product prior to
being marketed in Canada. It uniquely identifies
all drug products sold in a dosage form in
Canada and is located on the label of prescription
and over-the-counter drug products that have
been evaluated and authorized for sale in
Canada.

» SNOMED CT
› SNOMED CT (Systematized Nomenclature of
Medicine -- Clinical Terms), is a systematically
organised computer processable collection of
medical terminology covering most areas of
clinical information such as diseases, findings,
procedures, microorganisms, substances, etc.

» LOINC
› Logical Observation Identifiers Names and Codes
(LOINC) is a database and universal standard for
identifying medical laboratory observations. It
was developed and is maintained by the
Regenstrief Institute, a US non-profit medical
research organization, in 1994.

» ICD-10
› The International Statistical Classification of
Diseases and Related Health Problems, 10th
Revision (known as "ICD-10") is a medical
classification list for the coding of diseases, signs
and symptoms, abnormal findings, complaints,
social circumstances, and external causes of
injury or diseases, as maintained by the World
Health Organization (WHO).

Implementation Considerations
» Change and Lifecycles
» Just because a standard exists, doesn’t mean
that it never changes
› Country codes
• Example: Sint Maarten

More on Lifecycle
» Some code values are bound to different pan-
Canadian standards releases.
» A jurisdiction that implements a prior release
should use the previous codes
» On the other hand, some code systems are
updated regularly
› e.g.: ClinicalDrug
• The list of drug products managed by Health
Canada is updated every quarter
» There’s no formal distinction of these code
categories

Mapping
» At Partnership, it’s not uncommon to hear
jurisdictions talk about “implementation”
› What they’re often talking about is code mapping
» In the target architecture, Accenture plans to
use a HLI to provide mapping services
› Don’t assume that mapping is a trivial exercise
› Some concepts don’t map neatly

Final Recap
» Concepts
» Code Data Types
» Concept Domains, Code
Systems and Value Sets

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