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About Search & Browse

NGC's search engine is a state-of-the-art tool designed for sophisticated collections of medical information. It runs in conjunction with a layer of semantic metadata that has been applied to Clearinghouse content which, though written by multiple developers and derived from many resources, are completely integrated and connected by these topic-based medical language tags from the Unified Medical Language System (UMLS), developed by the National Library of Medicine (NLM). Visit the FAQ to learn more about UMLS and for answers to specific search-related questions.

Main Search Engine

The main search engine is accessed via the search box on the home page or in the masthead. It is not case-sensitive.

This search engine operates by seeking matches with search terms from two distinct types of data pulled from the contents of NGC: a layer of semantic metadata associated with a content piece and the exact matches of words or phrases in the text. Semantic matches are those based on the meaning of the search terms and the concepts they describe, allowing the user to find pertinent information without having to search for all synonyms of a given search term. To supplement these semantic results, the search engine provides all guideline summaries, expert commentaries, and guideline syntheses that contain exact matches to the search terms.

In other words, when the user enters a search term, all variants of the term are considered in all contexts. Results are then ranked by a robust algorithm to ensure that the most relevant documents are delivered first. Following is a simplified template for the code driving the search engine:

search term --> [documents indexed with term OR equivalent(s)/variant(s)] OR 
	            [documents containing all words found in term OR equivalent(s)/variant(s)]

For example:

diabetes --> SEMANTIC: documents indexed with diabetes OR diabetes mellitus type 1 OR 
	            [other equivalents/variants] --> FULL TEXT: documents containing diabetes OR 
	            diabetes mellitus type 1 OR [other equivalents/variants]

Then, semantic and full-text results are combined and sorted according to a ranking algorithm that determines relevance.

Supporting Features

The following features complement semantic and full-text searching:

Feature Description Example
Word or concept search Enter a word or multi-word concept to receive both index and full-text matches. A thesaurus is used to accommodate searches for synonyms, abbreviations, and other equivalents. Searches for chronic obstructive pulmonary disease and COPD find all documents indexed with that concept or that feature either term in their text.
Phrase search Multiple words are considered together with an implied AND operator. diabetes insulin includes documents indexed with these terms as well as documents containing both words
Disambiguation Disambiguation terms are presented when the search term matches more than one index term. Clicking a disambiguation term performs a search within the original query' results. diabetes includes options for diabetes mellitus, diabetes mellitus type 1, and diabetes mellitus type 2
UMLS concept unique identifier (CUI) number Enter a single CUI number for exact match only (no Boolean, no truncation). C0014544 yields results for Epilepsy
SNOMEDCT code Enter a single SNOMEDCT code for exact match only (no Boolean, no truncation). 73211009 yields results for diabetes mellitus
ICD9CM code Enter a single ICD9CM code for exact match only (no Boolean, no truncation). E928.9 yields results for unspecified accident
UMDNS code Enter a single UMDNS code for exact match only (no Boolean, no truncation). 15-784 yields results for stents
Document number Locate a specific guideline summary by document number by searching for ## followed by the number. This special notation bypasses index or full-text searching and looks for the exact document number. ##5244

The following features complement full-text searching:

Feature Description Example
Thesaurus expansion Full-text searching considers the search term and its equivalents (synonyms, abbreviations). doctor also includes physician
Stemming The stemming function considers a word’s conjugations and singular/plural forms. book also includes books and booked
Boolean operator AND AND searches for documents containing both words/phrases in any order. schizophrenia AND anxiety
Boolean operator OR OR searches for documents containing either word/phrase, possibly both. schizophrenia OR anxiety
Boolean operator NOT NOT searches for the first word to the exclusion of the second word/phrase. schizophrenia NOT anxiety
Single-set quotation marks Results are limited to the exact word/phrase when it is enclosed in quotes. Punctuation inside the quoted phrase is ignored; stemming and thesaurus expansion are not performed. Note: The use of quotation marks bypasses the semantic piece of the search engine. "gastric bypass"
Simple Boolean combination Combinations of Boolean operators and quotes can be used. Morbi
Parenthetical Boolean combination Parentheses instruct the search engine to consider the order of operators. "gastric bypass" AND obesity
Parenthetical Boolean combination Parentheses instruct the search engine to consider the order of operators. (bipolar disorder AND antidepressants) OR valproic acid
bipolar disorder AND (antidepressants OR valproic acid)
Truncation Use truncation to expand retrieval. The search engine will return words that match the characters up to the truncation character. Truncation characters may only be used at the end of the word root. diabet* (not *etic)

In addition, the search engine includes the following functionality:

  • The user may narrow browse or search results using facets in the left rail.
  • Options to sort by relevance (default) or date are provided on search results pages. Sorting by date disregards the relevancy ranking.
  • When viewing a guideline summary, the user may run a search on a UMLS concept by clicking on the term inside the Classification tab. This is an index-only search, meaning full-text results are not included.
  • The user may use hyphens to generate results dependent on punctuation.

Page Last Reviewed or Updated: July 15, 2016