Units of Measure

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Units of Measure
Cecil Lynch, MD, MS Mary Cooper CTMS Lab
Interface SIG 1/31/2006
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Discussion Topics

• Lab Interface SIG Recommendations
• Units of Measure should encompass all areas of
  clinical medicine and not be limited to Lab,
  Pharmacy, Adverse Events, etc.
• Units of Measure will be represented by the
  Unified Code for Units of Measure (UCUM).
• After presentation to CTMS there will be a 2 week
  comment period for CTMS members to respond.

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Use Case Analysis

• Purpose of collecting UoM data
• Assessment
• Analysis
• Identification
• Interoperability
• Use/Applications
• Laboratory (Test result values and reference
  ranges)
• Pharmacy (Agent Dose)
• Radiology (Diagnostic Imaging)
• Adverse Event Reporting
• Non-Clinical Measurements (ex. Time)

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High Level Usage/Relevant Standards

• Applicable External Standards which reference
  Units of Measure
• ANSI X12
• HL7 v2
• HL7 v3 RIM
• ISO
• IUPAC
• DICOM
• The majority of current external standards use an
  atomic classification system based on the Unified
  Code for Units of Measure (UCUM).
• Other standards applications represent units of
  measure as a bulk list.

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Description of UCUM
Unified Code for Units of Measure
(UCUM) http//aurora.regenstrief.org/UCUM/ucum.htm
l UCUM is heavily based on ANSI X3.50-1986, ISO
2955-1983, and HL7 extensions ISO. Basic set
of terminal symbols unit atoms Includes a code of
multiplier prefixes and business rules for
algebraic expression. Tables kind of
quantity (Mass, Length, etc.) applicable use (SI
Units, Units Used Predominantly in Clinical
Medicine)
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Other Reasons for UCUM
Notice Consolidated Health Informatics (CHI)
Initiative Health Care and Vocabulary Standards
for Use in Federal Health Information Technology
Systems Federal Register December 23, 2005
(Volume 70, Number 246) Page 76287-76288 Units
of Measure. Standard HL7 Version 2.X. (UCUM)
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Its The Law

• IV. Impact Statement
• The Federal government will require all
  future health information technology system
  acquisitions to be based on CHI standards when
  applicable, whether system development occurs
  within the Agency or through the use of
  contractor services.

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Proposed Data Element

• One Units of Measure CDE
• Data Element Concept (reused)
• Value Domain referenced to UCUM

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RecommendationsUnits of Measure UCUM Codes
Data Element Concept Units of Measure Public ID
2013051v3 (reused from CCR)
Data Element Units of Measure UCUM Codes Public
ID 2423412
Value Domain UCUM Codes Public ID
2423409 http//aurora.regenstrief.org/UCUM/ucum.h
tml
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Recommendation DetailsUnits of Measure UCUM Code
Units of Measure Definition Standard used to
express the size or magnitude of something.
Units of Measure UCUM Codes Definition The code
that represents the determinate amount or
quantity used as the standard of measurement for
the size, magnitude or capacity of something.
UCUM Codes Definition A code system of
symbols and rules that represents the size,
magnitude or capacity of a determinate amount
or quantity used as the standard of measurement
for international science, engineering, and
business.
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HL7 v3 and UCUM

• Coded Simple Value (CS) specializes CV
• Definition      Coded data in its simplest form,
  where only the code is not predetermined. The
  code system and code system version are fixed by
  the context in which the CS value occurs. CS is
  used for coded attributes that have a single
  HL7-defined value set.
• CS can only be used in either of the following
  cases
• for a coded attribute which has a single
  HL7-defined code system, and where code additions
  to that value set require formal HL7 action (such
  as harmonization.) Such coded attributes must
  have type CS.
• for a property in this specification that is
  assigned to a single code system defined either
  in this specification or defined outside HL7 by a
  body that has authority over the concept and the
  maintenance of that code system. (This is the
  case of UCUM)
• For CS values, the designation of the domain
  qualifier will always be CNE (coded,
  non-extensible) and the context will determine
  which HL7 values to use.

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UCUM in Application Use

• The patients height is 72 inches.
• UCUM expression for inches is in_i 
• Not user friendly
• Very computable
• HL7 allows translation to a more friendly
  presentation

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HL7 V3 Messaging of UCUM

• Physical Quantity (PQ) specializes QTY
• Definition      A dimensioned quantity
  expressing the result of measuring.
• value REAL The magnitude of the quantity measured
  in terms of the unit.
• unit CS The unit of measure specified in the
  Unified Code for Units of Measure (UCUM)
  http//aurora.rg.iupui.edu/UCUM.
• translation SETltPQRgt An alternative
  representation of the same physical quantity
  expressed in a different unit, of a different
  unit code system and possibly with a different
  value.

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HL7 Example
ltObservation classCode"COND"gt ltcode
codeSystem"2.16.840.1.113883.6.5.96"
code"248333004" displayName"standing height"
/gt ltvalue xsitype"PQ" value"72"
units"in_i"gt lttranslation
xsitype"PQR"gt ltcodeSystem"2.16.840.1.113883.
6.5.96" code"258677007" displayName"in -
inch" originalText"inches"/gt lt/translationgt lt/
valuegt lt/Observationgt
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Discussion Summary

• Decisions
• Action Items
• Comment period of 2 weeks.
• Outstanding Issues
• Next steps and meeting dates
• Review comments with Lab SIG.
• Present proposal to VCDE workspace.