# Extended Searches

Extended searches enable the search to return more candidate matches. The intention of extending searches is to maximize the likelihood that the required Concept or Description will be included in the candidate matches. This sub-section describes some recommended techniques for extending searches.

## Extend Search by Word Equivalents

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 but equivalent word is used in the search.

SNOMED CT cannot and does not attempt to enumerate all possible *synonyms* for all Concepts. Neither to enumerate all possible semantically equivalent typographic, part-of-speech or ordering variations of the synonyms it does include. To do so, especially automatically, would both require a considerable lexical resource and hugely increase the number of Descriptions and the size of any associated index tables. An alternative technical architecture involves a selective, logical expansion of search expressions and the relevant fragment of Description-space at run-time, using substantially the same lexical resources

For example: <mark style="color:blue;">|</mark> Kidney stone <mark style="color:blue;">|</mark> and <mark style="color:blue;">|</mark> Renal calculus <mark style="color:blue;">|</mark> are synonymous Descriptions in SNOMED CT. However, a search of SNOMED CT for the target phrase "kidney stone fragmentation" yields the result <mark style="color:blue;">|</mark> Percutaneous nephrostomy with fragmentation of kidney stone <mark style="color:blue;">|</mark> while a search for "Renal stone fragmentation" yields no results. One way of addressing this problem is to maintain a table of *word equivalents, and* a table of this type is a prerequisite for exhaustive synonym generation.

Individual implementers will wish to add additional *word equivalents* to meet the requirements of their particular medical specialty or user needs. The resulting table then acts as an additional resource to assist searching and parsing of phrases. It need not be a comprehensive dictionary of words.

{% hint style="info" %} <mark style="background-color:red;">The Word Equivalent Table can be found in the Lexical Resources folder, which is available from the</mark> <mark style="background-color:red;">**Technical**</mark> <mark style="background-color:red;">**Resources**</mark> <mark style="background-color:red;">in the</mark> <mark style="background-color:red;">**Document Library**</mark><mark style="background-color:red;">.</mark>
{% endhint %}

### 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.

### 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.

Word Equivalents Table Example

<figure><img src="https://655065570-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCEAcChvWjWEu16YmwNrz%2Fuploads%2Fgit-blob-a7cc505060a15eb72559a5afd93e9a25d35a47dc%2F33490616.png?alt=media" alt=""><figcaption></figcaption></figure>

<figure><img src="https://655065570-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCEAcChvWjWEu16YmwNrz%2Fuploads%2Fgit-blob-0788e20e116fe85555b8b75879aa275e4ccf3b30%2F33490617.png?alt=media" alt=""><figcaption></figcaption></figure>

<figure><img src="https://655065570-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCEAcChvWjWEu16YmwNrz%2Fuploads%2Fgit-blob-18cd6af1d67410bb0e9211dc63f5fdfff78d4e3c%2F52171324.png?alt=media" alt=""><figcaption><p>Extending searches with word equivalents - step 1</p></figcaption></figure>

The user selects this option (or it is invoked automatically because the initial search without word equivalents found nothing) and searches again using the same search *string*. The table is used to make substitutions in the search *string* to produce all possible unique search variants:

* "Fragmentation of renal calculus"
* "Fragmentation of renal stone"
* "Fragmentation of kidney stone"
* "Fragmentation of kidney calculus"
* "Fragmentation of Nephrolith"
* "Fragmentation of renal calculus"
* "Fragmentation of renal calculi"
* "Fragmentation of kidney calculi"

These 8 search variants are used as the target phrases for the searches. The search results of these variants are combined, duplicate Concepts are eliminated and the list of search results is returned.

<figure><img src="https://655065570-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCEAcChvWjWEu16YmwNrz%2Fuploads%2Fgit-blob-f8f8efdbfd9d322ea6e7792cf852f98f39b841da%2F52171323.png?alt=media" alt=""><figcaption><p>Extending searches with word equivalents - step 2</p></figcaption></figure>

## Extend Search by Postcoordinated Searching

A SNOMED CT search can be expanded to support appropriate or commonly used qualifiers. This technique is useful in situations where searches fail to find a precoordinated Concept. This is particularly useful in clinical applications which support the storage of postcoordinated expressions. This technique is likely to increase the ease of entry of postcoordinated expressions in the clinical record as well as the overall usability of search and data entry.

As a basic implementation, a limited facility for recognizing commonly qualifying words may be used. For example, Concepts such as <mark style="color:blue;">|</mark> left <mark style="color:blue;">|</mark>, <mark style="color:blue;">|</mark> right <mark style="color:blue;">|</mark>, <mark style="color:blue;">|</mark> routine <mark style="color:blue;">|</mark>, and <mark style="color:blue;">|</mark> emergency <mark style="color:blue;">|</mark> are applicable as qualifiers for some Concepts when not already included in a precoordinated Concept.

### Example:

The phrase "emergency closed reduction fracture left femur" might list "closed reduction of fracture of femur, emergency, left" which refers to the postcoordinated expression

```
112777008 |closed reduction of fracture of femur| : 
260870009 |priority| = 25876001 |emergency| , 272741003 |laterality| = 7771000 |left|
```

<figure><img src="https://655065570-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCEAcChvWjWEu16YmwNrz%2Fuploads%2Fgit-blob-89d9748f4f3c59913437dcfe6629112e6eb25605%2F52171326.png?alt=media" alt=""><figcaption><p>Extending searches by post-coordination - step 1</p></figcaption></figure>

<figure><img src="https://655065570-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FCEAcChvWjWEu16YmwNrz%2Fuploads%2Fgit-blob-3aec5487929ff129dd9feb2ab222421b5ef1498e%2F52171327.png?alt=media" alt=""><figcaption><p>Extending searches by post-coordination - step 2</p></figcaption></figure>

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# Agent Instructions: Querying This Documentation

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```
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```

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