Home-Grown Coding Systems

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Home-Grown Coding SystemsA Critical Step in EMR
Implementation

• Eric Rose, MD
• Associate Director for Clinical Informatics
• Information Systems Department
• University of Washington Physicians Network
• http//faculty.washington.edu/momus/

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SUMMARY

• Implementation of any EMR (including
  vendor-supplied) requires the that the user
  institution create coding systems
• This can be done well or badly
• It matters

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Some definitions

• Concept an idea encompassing a class of objects
  ("unit of knowledge created by a unique
  combination of characteristics"-ISO)
• Term A word denoting a concept
• Terminology/Controlled Vocabulary/Ontology a set
  of terms pertaining to a given domain, not
  necessarily with any structure
• Nomenclature A terminology structured
  systematically according to pre-established
  naming rules (ISO)

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Some definitions (contd)

• Coding system A terminology context-free
  symbolic codes for each term
• Classification/taxonomy A terminology system
  specified relationships between terms (concept
  system-ISO 1087-1)

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What is a coding system and what does it do?

• Represents in a standardized fashion
• Groups
• Separates
• Abbreviates
• Facilitates automated data-processing
  transmittal

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Types of coding systems

• Simple, 1-1 (CA, NY, TX)
• Categorical (record store bins)
• Hierarchical (homo sapiens)
• Multiaxial (Dewey-decimal, SNOMED)

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What does this have to do with EMR Implementation?
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THE UNIVERSE OF CONCEPTS
READ
LOINC
NANDA
SNOMED CT
CPT
ICD-10
NDC
ICD-9-CM
NCPDP
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What does this have to do with EMR Implementation?

• Most EMRs allow customized choices for various
  database items
• Each one of these is a small coding system

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What does this have to do with EMR
Implementation? (contd)

• If developed carefully, home-grown coding systems
  facilitate
• Intuitive data entry
• Interpretable data _at_ individual patient level
• Usable data at population level
• Usable data for automated decision-support
  systems
• Data that is shareable with other systems

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Examples of mini-coding systems you might need to
create

• Disease Categories for Family History
• Reason for Visit
• Allergic Reaction Type
• Delivery Outcome
• Anesthesia Type for Surgery
• Source of Diagnostic Specimens
• Ethnic Group
• Marital Status

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What makes a coding system good?

• Completeness
• Nonredundancy
• Clarity
• Stability
• Granularity appropriate to use or flexible
• Evolutionary
• (Adapted from Cimino, 1998 Chute et al., 1998)

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Completeness

• There should be a term for any possible situation

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CompletenessExampleReason for Medication
Discontinuation

• Allergic response
• Alternate therapy
• Availability
• Cost of medication
• Discontinued by another Health Care Provider
• Discontinued by patient
• Dose adjustment
• Duplicate
• Error
• Ineffective
• NON Covered Medication
• Paradoxical response
• Pregnancy
• Prescription never filled
• Reorder
• Resistant Organism
• Side effects
• Therapy completed
• What if medication was never taken by patient?
  No way to denote that!

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Nonredundancy

• There should be only one term for any given
  situation

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Nonredundancy-ExampleNext of Kin-Relationship to
patient

• Domestic Partner
• Life Partner
• Partner
• Significant Other

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Clarity

• The categories in your coding system should be
  unambiguous to all users

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Clarity-Examples

• Family Medical History category Blood Disease,
  Anesthesia
• Medication reason-for-d/c Alternative Therapy,
  Error

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Stability

• Once defined, the meaning of a code must not be
  changed, though it may be inactivated so it is
  not applied to any new cases

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Appropriate or Flexible Granularity

• Granularity Level of detail described by the
  coding system, i.e. fineness of categorization
• Low granularity Few, broad categories
• High granularity Many, narrow categories

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Appropriate Granularity-ExamplesFamily History
categories

• Alcohol dependency, Drug dependencyIt is
  sufficient to just have one category for
  Chemical Dependency
• Heart disease-Not granular enough to meet needs
  of risk assessment for coronary disease

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Evolutionary

• Coding system development is an ongoing process,
  requiring addition of new categories and
  inactivation of old ones to keep the system
  congruent with prevailing ideas.
• Example Family History category, Venous
  Thrombosis

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Guiding principles

• CENTRALIZE control of the coding system
• Keep your lists SHORT
• Respond PROMPTLY to user requests for additions
  and explain rationale when its not appropriate
  to meet the request
• Design for the future including new user types
  interfaces
• Careful with Other

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For further reading

• Bakken S et al. Toward Vocabulary Domain
  Specifications for Health Level 7-coded Data
  Elements. JAMIA 7333-342, 2000.
• Cimino JJ. Desiderata for controlled medical
  vocabularies in the twenty-first century.
  Methods Inf Med. 1998 Nov37(4-5)394-403
• Chute CG. Cohn SP. Campbell JR. A framework for
  comprehensive health terminology systems in the
  United States. JAMIA 5(6)503-10, 1998 Nov-Dec.
• ISO 1087-12000. Terminology Work-Vocabulary-Part
  1 Theory and Application