Units of Measure

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

2. 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.

3. 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)

4. 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.

5. Description of UCUM Unified Code for Units of Measure (UCUM) http://aurora.regenstrief.org/UCUM/ucum.html 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)

6. 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)

7. It’s 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.

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

9. 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.html

10. 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.

11. 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.

12. UCUM in Application Use • The patient’s height is 72 inches. • UCUM expression for inches is [in_i]  • Not user friendly • Very computable • HL7 allows translation to a more friendly presentation

13. 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 SET<PQR> 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.

14. HL7 Example <Observation classCode="COND"> <code codeSystem="2.16.840.1.113883.6.5.96" code="248333004" displayName="standing height" /> <value xsi:type="PQ" value="72" units="[in_i]"> <translation xsi:type="PQR"> <codeSystem="2.16.840.1.113883.6.5.96" code="258677007" displayName="in - inch" originalText="inches"/> </translation> </value> </Observation>

15. 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.