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Best Practices for Interoperable Data Exchange Using LOINC

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					Best Practices for Interoperable
  Data Exchange Using LOINC
      Ming-Chin (Mark) Lin, MD
        Stanley M. Huff, MD
                Introduction
• Two primary use cases
  – Sharing data between and among different
    institutions for patient care
  – Aggregating data between and among different
    institutions for clinical research, quality
    improvement, public health surveillance, etc.
    (secondary use)
• Use LOINC codes as the lingua franca for the
  data sharing
          Introduction (continued)
• Mark’s work comparing LOINC usage across ARUP,
  Regenstrief, and Intermountain
• What is truth?
   – If local codes from different sites are mapped to the same LOINC
     code, how do we know they are really the same test?
   – If local codes from different sites are mapped to different LOINC
     codes, how do we know they are really different tests?
• Extensional definitions
   – Comparison of names (substance, timing, property, specimen),
     units of measure, mean value, standard deviation, coded values,
     co-occurring tests, etc.
• Results: We found about a 4% error rate in mapping
   – And that is us! What is it like for “regular” facilities?
       Introduction (continued)
• Analyzing the errors lead to additional
  questions
  – Can we classify the errors?
  – What is the ultimate goal of mapping?
  – Can we define “best practices” for mapping so
    that everyone doing mapping can achieve greater
    accuracy?
  “Fit for Purpose” or “Good Enough”
                mapping
• Example: Tests with a method specified at site
  A are mapped to methodless tests at site B
• Works for the known use case
  – Either estimated weights or scale weights may be
    good enough for a particular study
• This represents a loss of information when
  data moves from A to B
        Proposed Best Strategy
• Always map to the LOINC code or combination of
  codes that capture all known information about
  the test
  – Always capture the method in the data if it is known
• Rationale: All uses of the data (especially
  secondary uses) are not known at the time of
  initial mapping or data collection
• “Fit for Purpose” mappings will preclude
  secondary use of the data in some situations
  – What if you want to study whether two different test
    methods are truly equivalent?
       Degrees of Interoperability
• Degree I: Exact equivalence without translation
   – Same code, unit of measure, and value set
   – Data are mutually substitutable in all contexts of use
• Degree II: Exact equivalence after translation
   – Unit of measure conversion (need UCUM)
   – Mass concentration to substance concentration conversion
     (need the molecular weight)
   – Pre and post coordination translation
       • Method as part of LOINC code versus method sent somewhere else in
         the message
       • Peak or trough as part of LOINC code versus peak and trough sent
         somewhere else in the message
   – Data are mutually substitutable in all contexts of use after
     translation
 Degrees of Interoperability (cont)
• Degree III: Context specific subsumption
  – A parent-child relationship exists between tests at
    the different institutions
     • Method specific tests roll up to methodless tests
     • IgM or IgG antibodies roll up to generic antibody
  – Data are mutually substitutable only in a specific
    context of use even after translation
• Degree IV: No interoperability
  – No comparable data or information exists
    between or among institutions
Examples
                    Proposal
• Create specific best practice mapping guidelines
  for difficult situations and common errors
• Examples
  – How to deal with variable granularity in methods
  – How to deal with pre and post coordinated specimen
    type
  – How to deal with pre and post coordinated challenge
    conditions
  – Use of Acnc and Titr
   Example Guideline for Method
• If possible, and the method is known, map to the
  methodless LOINC code and always send the
  method in some other part of the message
  – Related policy: the LOINC committee will make all
    needed methodless LOINC codes
• If the method is known but it is not possible to
  post coordinate the method, map to the method
  specific pre coordinated LOINC code
• If the method is not known, map to the
  methodless LOINC code
Example Guideline for Interpretations
• Always map to the quantitative LOINC code
   – Related policy: The LOINC Committee will discourage
     or deprecate the use of nominal or ordinal LOINC
     codes for concentrations
• Send numbers when they exist as the value of
  OBX 5
• Send interpretations when they exist as the value
  of OBX 8
• One or the other or both of the numeric value
  and the interpretation can exist in a data instance
Discussion

				
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posted:2/20/2013
language:English
pages:13