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). Read 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)]
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.
|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.
||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 terms are presented when the search term matches more than one index term. Clicking a disambiguation term performs a search within the original query's 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).
||C0206515 yields results for vaccines, conjugate
||Enter a single SNOMEDCT code for exact match only (no Boolean, no truncation).
||73211009 yields results for diabetes mellitus
||Enter a single ICD9CM code for exact match only (no Boolean, no truncation).
||E928.9 yields results for unspecified accident
||Enter a single UMDNS code for exact match only (no Boolean, no truncation).
||15-784 yields results for stents
||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.
The following features complement full-text searching:
||Full-text searching considers the search term and its equivalents (synonyms, abbreviations).
||doctor also includes physician
||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.
|Simple Boolean combination
||Combinations of Boolean operators and quotes can be used.
||"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 considers forms of a word prefix (not suffix).
||diabet* (not *etic)
In addition, the search engine includes the following functionality:
- The user may search within browse or search results.
- Options to sort by relevance (default) or date are provided on search results pages. Sorting by date removes the relevancy ranking.
- Spelling suggestions are provided when a search term is spelled incorrectly. Clicking a suggested word performs a search on that term.
- 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.
- Words found within the body of a document are highlighted when the user navigates to the document from a search results page. (The highlighting function looks for words anywhere in the document, operating independently from the order typed into the search box. In some instances, the highlighted word may be part of a longer word.)
- The user may use hyphens to generate results dependent on punctuation.
Advanced Search leverages the power of the main search engine while also allowing the user to select specific subsets of Guideline summaries. The total data set is narrowed as the user selects checkboxes, with the resulting number of documents displayed on the page before a search is conducted (Note: Keyword search results are not included in this count). Entering a keyword is optional, though checking at least one box is required. All values available for selection will yield at least one result. Index-only searches may be run on MeSH terms (as are used on By Topic browse) by selecting the Disease or Condition, Treatment or Intervention and Health Services Administration checkboxes.