Proposal for Representing SNOMED CT Assessment Scales in HL7 V3

Proposal for representing SNOMED CT Assessment Scales in HL7 V3

A convention for modeling assessment scales in HL7 V3 has been made by the Patient Care Technical Committee in the Care Structures Topic of the Care Provision Domain. The next step for the Patient Care TC is to add the vocabulary mapping step to the model for multiple vocabularies. Since SNOMED CT is the most expressive of the vocabularies, the SNOMED vocabulary model and the work on representing assessment scales in SNOMED CT by the SNOMED Nursing Work Group is being examined first. Since TermInfo is also examining the relationship between HL7 models and SNOMED CT, this examination is being sent to the TermInfo Project for review and comment.

This examination begins from several foundations:

• HL7 RIM concepts found in current documentation and the original USAM formulations
• ISO Nursing Terminology Models
• Nursing Terminology Summit evaluations
• SNOMED CT hierarchies for scale elements, as suggested by the SNOMED Nursing Working Group
• Role relations for procedures under consideration by SNOMED

These foundations won’t be reviewed in this document, which leaves open the possibility that some beliefs about these foundations are not really shared by the readers. However, the hope will be to discover where these beliefs differ between the readers and flesh out the document to disambiguate the beliefs represented.

Assumptions:

• ISO Nursing Terminology Models’ Action Class includes Observations as well as other procedures

• SNOMED procedure hierarchy terms may be used in the ISO Nursing Terminology Models’ Action Class

• SNOMED Observable Entity terms may be used in the ISO Nursing Terminology Models’ Focus class

• HL7 Act Class is used to represent Actions including Observations

• HL7 Act.methodology attribute represents an Act “has methodology” relationship that should only be used when the methodology is not adequately specified in Act.Code

• HL7 does not directly specify a “has focus” relationship. Instead, the ISO Nursing Terminology Model “Action has focus Focus relationship” is expressed within the HL7 Act.Code concept (a conclusion announced by the TermSum Interventions group and presented at AMIA Fall Conference)

• Finding in SNOMED is synonymous with the phrase “result of an observation”

• In HL7 “Result of an Observation” may map to Observation.value where value may be any datatype including Text, Numbers or Codes (for better or for worse--?modify?)

• In HL7, Observation.InterpretationCode is used to both “interpret observation.value” or “represent a coded result or finding” (for better or for worse--?modify?)

• In an assessment scale like a generic Likert scale, the numeric value scale is often defined by an ordinal text value scale and vice versa. In other words, the Likert scale sets up an equivalence of meaning between text and arithmetic numbers(meaning they can be added, multiplied, etc.)

• Assessment scales may also include one or more Likert scales. In this situation, the number values may be added or averaged according to a formula to achieve a total score. In addition, the total score may be related to a Likert scale model for interpretation of the total score. Examples include Apgar, Barthel, etc.

These assumptions are used to create mappings between SNOMED terms, ISO Nursing Terminology Models, and Likert scale models (including additive Likert scales) in the following figure:

• The administration of the assessment appears in the procedure hierarchy
• The name of the assessment scale should appear in the staging & scales hierarchy with an hasMethod roleRelationship from procedure
• The individual observations (items) comprising a scale should appear in the observable entity hierarchy with a hasFocus roleRelationship from Procedure
• The CodedScore of each assessment item should appear in the clinical finding hierarchy with hasFinding roleRelationships from Observable Entity and from Procedure

The diagram illustrates the relationships between elements of assessment scales and the SNOMED CT hierarchy suggested by the modeling policy for each element. The assessment item elements, like tests within a standard laboratory battery (i.e.: Chem 7, Chem 12…), are repeated. Each assessment item score would be ‘evaluated’ per the assessment scale algorithm and arithmetically processed, representing an ‘overall score’ under the Scalescore with an associated Codedscore finding.

From this model, SNOMED terms may be mapped into a spreadsheet. The first example will use the Barthel Index. The following is a form (paper-based) version of the Barthel Index

The BARTHEL INDEX

Activity / Score
Feeding
0 = unable
5 = needs help cutting, spreading butter, etc., or requires modified diet
10 = independent / 0 5 10
Bathing
0 = dependent
5 = independent (or in shower) / 0 5
Grooming
0 = needs to help with personal care
5 = independent face/hair/teeth/shaving (implements provided) / 0 5
Dressing
0 = dependent
5 = needs help but can do about half unaided
10 = independent (including buttons, zips, laces, etc.) / 0 5 10
Bowels
0 = incontinent (or needs to be given enemas)
5 = occasional accident
10 = continent / 0 5 10
Bladder
0 = incontinent, or catheterized and unable to manage alone
5 = occasional accident
10 = continent / 0 5 10
Toilet Use
0 = dependent
5 = needs some help, but can do something alone
10 = independent (on and off, dressing, wiping) / 0 5 10
Transfers (bed to chair and back)
0 = unable, no sitting balance
5 = major help (one or two people, physical), can sit
10 = minor help (verbal or physical)
15 = independent / 0 5 10 15
Mobility (on level surfaces)
0 = immobile or < 50 yards
5 = wheelchair independent, including corners, > 50 yards
10 = walks with help of one person (verbal or physical) > 50 yards
15 = independent (but may use any aid; for example, stick) > 50 yards / 0 5 10 15
Stairs
0 = unable
5 = needs help (verbal, physical, carrying aid)
10 = independent / 0 5 10
TOTAL (0 - 100) / ______

The following is an example of a fully mapped Barthel Index. For illustration purposes the color of the table rows corresponds to a hierarchy where the SNOMED CT concept resides. In our example, yellow rows are procedures, green are staging & scales, blue are observable entities and pink are findings.

SCT Hierarchy / SCT Concept ID / SCT Description ID / SCT Term / Coefficient
Functional Assessment / Procedures / 12894003 / 22109015 / functional assessment
Barthel Index (has method) / Staging & Scales / 273302005 / 408608011 / Barthel index
Barthel index score (has focus) / Observable Entity / C133683 / Barthel index score
seriously limited / Finding / 0 to 9
moderately limited / Finding / 10 to 19
independent / Finding / 20 to 100
Feeding / Observable Entity / 165221002 / 256929016 / feeding ability
unable / Finding / 129052001 / 207756010 / feeding dependent / 0
needs help cutting, spreading butter, etc., or requires modified diet / Finding / 165223004 / 256931013 / needs help with feeding / 5
independent / Finding / 129044004 / 207748012 / feeding independent / 10
Bathing / Observable Entity / 288469009 / 428118013 / ability to perform washing and drying activities
dependent / Finding / 129043005 / 474719016 / Dependent for bathing / 0
independent (or in shower) / Finding / 129041007 / 474718012 / Independent bathing / 5
Grooming / Observable Entity / 165225006 / 256933011 / ability to perform grooming activity
needs to help with personal care / Finding / 165226007 / 256934017 / dependent for grooming / 0
independent face/hair/teeth/shaving (implements provided) / Finding / 165227003 / 256935016 / independent for grooming / 5
Dressing / Observable Entity / 284967006 / 423842012 / ability to perform dressing activity
dependent / Finding / 129065005 / 474726016 / dependent for dressing / 0
needs help but can do about half unaided / Finding / 129039006 / 474717019 / needs help with dressing / 5
independent (including buttons, zips, laces, etc.) / Finding / 284968001 / 423843019 / able to perform dressing activity / 10
Bowels / Observable Entity / 406217005 / 2157915017 / bowel continence status
incontinent (or needs to be given enemas) / Finding / 72042002 / 502027016 / incontinence of feces / 0
occasional accident / Finding / 165230005 / 256943014 / bowels: occasional accident / 5
continent / Finding / 24029004 / 481790010 / bowels: fully continent / 10
Bladder / Observable Entity / 406218000 / 2157916016 / urinary continence status
incontinent, or catheterized and unable to manage alone / Finding / 165232002 / 1489736014 / urinary incontinence / 0
occasional accident / Finding / 165233007 / 256951012 / bladder: occasional accident / 5
continent / Finding / 45850009 / 494375010 / continent of urine / 10
Toilet use / Observable Entity / 284899001 / 423745018 / ability to perform toileting activities
dependent / Finding / 129078005 / 474729011 / dependent in toilet / 0
needs some help, but can do something alone / Finding / 129045003 / 474720010 / needs help in toilet / 5
independent (on and off, dressing, wiping) / Finding / 129062008 / 474724018 / independent in toilet / 10
Transfers (bed to chair and back) / Observable Entity / 165236004 / 1762560010 / chair/bed transfer ability
unable, no sitting balance / Finding / 165237008 / 256955015 / dependent: chair/bed transfer / 0
major help (one or two people, physical), can sit / Finding / 165238003 / 256956019 / able to sit: chair/bed transfer / 5
minor help (verbal or physical) / Finding / 165239006 / 256957011 / minimal help: chair/bed transfer / 10
independent / Finding / 165240008 / 256958018 / independent: chair/bed transfer / 15
Mobility (on level surfaces) / Observable Entity / 282148005 / ability to walk on flat surface
immobile or < 50 yards / Finding / 102491009 / 250474012 / immobile / 0
wheelchair independent, including corners, > 50 yards / Finding / 301576009 / 442933018 / able to mobilize using wheelchair / 5
walks with help of one person (verbal or physical) > 50 yards / Finding / finding related to ability to walk on flat surface with assistance / 10
independent (but may use any aid; for example, stick) > 50 yards / Finding / 282149002 / able to walk on flat surface / 15
Stairs / Observable Entity / 301581000 / 442944014 / ability to manage steps and stairs
unable / Finding / 301583002 / 442946011 / unable to manage steps and stairs / 0
needs help (verbal, physical, carrying aid) / Finding / 301586005 / 442950016 / difficulty managing steps and stairs / 5
independent / Finding / 301582007 / 442945010 / able to manage steps and stairs / 10

An instance of an assessment would have one set of assessment scale items for each of the item categories. Building on the work of the HL7 Care Provision TC in the May 2005 V3 ballot, a proposal for an implementation of an instance of a Barthel Index coded in SNOMED follows with the same colors as the earlier table.

Object Name / attributeName / Primary SNOMED CT Code / Primary SNOMED CT Term / has focus Observable Entity Code / has focus Observable Entity Term / has method SNOMED Code / has method SNOMED Term
Barthel Index
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 408608011 / Barthel Index (staging & scales)
derivationExp / SumScore Function
value / 40
interpretationCode / independent
Bathing
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 428118013 / ability to perform washing and drying activities (observable entity)
derivationExp / Null
value / 5
interpretationCode / 428211014 / able to perform washing and drying activities (finding)
Stairs
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 442944014 / ability to manage steps and stairs (observable entity)
derivationExp / Null
value / 0
interpretationCode / 282149002 / able to walk on flat surface
Dressing / Undressing
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 423842012 / ability to perform dressing activity (observable entity)
derivationExp / Null
value / 5
interpretationCode / 474717019 / needs help with dressing (finding)
Mobility
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 282148005 / ability to walk on flat surface(observable entity)
derivationExp / Null
value / 0
interpretationCode / 250474012 / immobile (finding)
Transfer
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 165236004 / chair/bed transfer ability(observable entity)
derivationExp / Null
value / 5
interpretationCode / 256956019 / able to sit: chair/bed transfer (finding)
Continence of Bowels
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 2157915017 / bowel continence status (observable entity)
derivationExp / Null
value / 10
interpretationCode / 481790010 / bowels: fully continent (finding)
Controlling Bladder
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 2157916016 / urinary continence status (observable entity)
derivationExp / Null
value / 0
interpretationCode / 1489736014 / urinary incontinence (finding)
Grooming
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 256933011 / ability to perform grooming activity (observable entity)
derivationExp / Null
value / 0
interpretationCode / 256934017 / dependent for grooming (finding)
Toilet Use
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 423745018 / ability to perform toileting activities (observable entity)
derivationExp / Null
value / 5
interpretationCode / 474720010 / needs help in toilet (finding)
Eating
classCode / Observation
moodCode / Event
code / 22109015 / functional assessment (procedure) / 256929016 / feeding ability (observable entity)
derivationExp / Null
value / 10
interpretationCode / 207748012 / feeding independent (finding)

The focal class is an observation event act, coded with a post-coordinated (CD data type) SNOMED CT procedure of Functional Assessment Administration that is modified with the name of the scale, Barthel Index. The focal act has a SumScore Function derivation expression with an integer score value and a post-coordinated SNOMED CT observable and finding for the interpretation code.

Each assessment scale item is a V3 observation event with a post-coordinated expression using the root SNOMED CT procedure code and the SNOMED CT observable entities. Assessment scale items have Null derivation expressions, an integer for the observation value and a SNOMED CT finding for the item interpretation. An alternate representation that allows expression for methodology for individual items adds a staging & scales concept to the item code field as follows:

<Observation Item>
classCode / Observation
moodCode / Event
code / SCT procedure / SCT observable entity / SCT
staging & scales
derivationExp / Null
value / ##
interpretationCode / SCT Finding

Issues to be discussed by TermInfo

1)Are the mapping assumptions correct?

2)Is the model of “Procedure hasMethodology hasFocus hasFinding correct”?

3)What are the implications of numeric and text equivalencies on other observation modeling decisions?

4)Should Observation.value and Observation.interpretationCode recommendations be made to HL7 to improve standardization of Finding representations?

Outstanding SNOMED Issues

1)Should Procedures in SNOMED support the hasMethod hasFocus hasFinding role relationships?

2)How to handle the gap analysis for SNOMED support of published assessment scales?