Overview

VA Lexicon is a set of vocabulary files used by VistA's Problem List, TIU (doc templates) and other packages. It's main job is to map from a keyword to an appropriate code. With the lexicon, a doctor doesn't pick ICD 9 codes: she picks key words and the Lexicon maps that word to appropriate standard concepts in the background - there are 36 coding systems with 475037 codes. ICD9 is the main scheme mapped to in VistA.

It seems that the Lexicon started off as a simple "synonym and plurals" gatherer, so that one "master label" could cover all variations of a word and be mapped once to appropriate codes. Then the VA layered on the concept of "meaning" (757_11: SEM CLASS, 757_12: SEM TYPE) which denoted the contexts of these "master labels", for example that something had one meaning in mental health and another elsewhere. This move from word-play to a sort of meta-thesaurus (think NCI Meta Thesaurus) isn't fully realized.

Two important notes:

  1. a look at FOIA VistA shows that the VA is moving toward SNOMED CT as its new meta thesaurus BUT rather than establish a new lexicon or mapping entries in the existing Lexicon, the VA appended SNOMED entries to the end of the existing Lexicon and these SNOMED concepts go unused. The addition of SNOMED means FIOA has 533874 concepts or high level labels and 1310456 (vs 156432 in pre-SNOMED VistA) expressions (labels for concepts).
  2. One other issue: the lexicon defines codes (ICDs, CPTs etc etc) but these specifications aren't linked to other definitions for the same codes elsewhere in VistA

Example Concept: Obesity

Concept
refs
Major Expression
Obesity Major
All expressions
5 ... synonyms, plural ...
Codes into Expression!
5
Semantic
Semantic Class. Physiology or a ... Note: code schemes appropriate under type (but crude: assumes simple code schemes)
Shortcut
Shortcut. Can't use "ADIPOSITY" in Problem List. Any tie back to Semantic Types? One short cut context, Problem List establishes two words (OVERWEIGHT and OBESITY) but only one, OBESITY, is in the expressions! (SNOMED has Overweight but ...). Note that shortcuts go to expressions! Seems like another overlay of labels. ie/ in app context, "overweight" goes to expression "obesity" but wasn't captured in expressions proper.

Example Concept: Alcohol Dependence

Major Concept
Alcohol Dependence and all its refs
MAJ Expression
Major Expression. There is always one. It has one shortcut (way to cut down on what expressions to offer). Note the supplemental of "ETOH".
Codes
757_02's, note that two ICDs, one for dependence, one for dependence continuous
Semantic Maps
two 757_1, both for class "Diseases/Pathologic Processes", one for type "Mental or Behavioral Dysfunction", one for type "Disease or Syndrome" [in inline then two semanticType, one semanticClass

Other exs

  1. Splint ie/ devices