SNOMED CT® Release Format 1 (RF1) Guide - ihtsdo

• Description104951019 is eliminated, it does not contain the word "1" or any word beginning with the
string "pyro".
4.4.1.3. Using word equivalents to enhance searches
In healthcare, there are many words with equivalent meanings. Synonyms provide alternative phrases referring
to the concept. However, synonyms are not created automatically for every possible combination of words
with an equivalent meaning. The success of simple searches using one or more keywords depends on the
text of the available descriptions.Therefore searches will fail or will be incomplete where a different equivalent
word is used in the search.
For example: "Kidney stone" and "Renal calculus" are synonymous descriptions in SNOMED CT. A search
of SNOMED CT for the target phrase "kidney stone fragmentation" yields the result "Percutaneous nephrostomy
with fragmentation of kidney stone," while a search for "Renal stone fragmentation" yields no results.
One way of addressing this problem is to maintain a table of word equivalents. A table of this type is a
prerequisite for exhaustive synonym generation. An initial set of word equivalents is included in the SNOMED
CT Developer Toolkit. Individual implementers will wish to add additional word equivalents to meet the
requirements of their particular medical specialty or user needs. This table is an additional resource to assist
searching and parsing of phrases. It need not be a comprehensive dictionary of words. Many searches can
be completed without reference to this table so it need not contain every word or equivalent phrase used in
SNOMED CT.
Several factors complicate the initial population and subsequent use of the word equivalents table:
• A phrase of two or more words may be equivalent to a single word.
Example:
"Endoscopic esophagus examination" is equivalent to "esophagoscopy"
• A word may have more than one meaning, and in this, only one meaning of a pair of words may be
equivalent. Thus an apparent enhancement of a search may in practice lose some of the specificity of the
intended search.
Example:
"Tap" and "aspiration" are equivalent in the context of terms such as "pleural tap", "pleural aspiration",
but not in the context of a "patella tap", a physical "tap" on a bag or catheter, or the clinical disorder
"neonatal aspiration syndrome."
• When searching using incomplete words and/or wildcards, use of word equivalents may impede effective
searches by increasing the number of spurious potential matches. This either extends the processing
required to filter the real matches from the potential matches or increases the length of the list of choices
presented to the user.
A wise system developer will allow the user to customize their search options, enabling searches to be
narrowed, or extended to meet the needs of varying circumstances.
4.4.1.3.1. Example: Using word equivalents table to extend a failed search
A system user enters the search string "Fragmentation of renal calculus;" the search returns no results. The
search application that the user has been provided with has the option to extend the search by using the
word equivalents table. The user selects this option and searches again using the same search string.
The word equivalents table contains the following relevant entries:
Terminology services Guide (RF1) | 315
© 2002-2012 International Health Terminology Standards Development Organisation CVR #: 30363434