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Subject Code Searching in Biomedical Databases

Magazine article Online

Subject Code Searching in Biomedical Databases

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Subject Code Searching In Biomedical Databases

Subject codes are the shorthand of online databases, whether the code or the codeword text is used. Most biomedical searchers are familiar with MeSH Tree Numbers used in MEDLINE. But the other large comprehensive files useful for biomedical searches, namely BIOSIS PREVIEWS, EMBASE Plus, and SciSearch, also utilize subject codes. This article will discuss the various types of subject codes used in these four databases as they are searchable on BRS, Data-Star (D-S), DIALOG, NLM, and ORBIT.

Just as free text is the modus operandi of end-users, subject codes are likely to be in the bag of tricks used by search intermediaries. Knowledge of how to search these codes is important. BRS recognizes this importance by devoting eight pages to code searching in their 1988 Biomedical Training Course Syllabus.

Subject codes are used to represent single subject descriptors, groups of descriptors, or broad subject concepts. Codes can be combined with each other to search for broad concepts, e.g., psychological aspects of cancer. Or they can be combined with free text to search for specific information such as "new" anti-hypertensive drugs. They can be used to limit searches to types of articles, geographic locations, or research study parameters. Entire categories of codes can be expanded by using truncation or a technique called exploding or cascading, which for this article will all be referred to as "explode". Sometimes the alphabetic, numeric, or alpha-numeric code and its accompanying codeword text are both searchable and explodable.

Additional shorthand called Chemical Abstracts Registry Numbers (RN) are assigned to chemical descriptors. In the case of articles which give the Enzyme Commission Number (EC) in the text of the article, this code is also searchable. These unique code numbers are easier to use than the many variations of most chemical names.


Registry numbers and EC numbers are easily used across databases on each databank, but subject codes used in BIOSIS, EMBASE, MEDLINE, and SciSearch are so unique and different from each other that cross-file searching is not advised. However, cross-file searching of all codes in companion databases and databases segmented by time periods is usually easy. MEDLINE companion files are AIDSLINE, AVLINE, BIOETHICS, CANCERLIT, HEALTH, POPLINE, and TOXLINE. EMBASE Drug Information is a subset of EMBASE. SciSearch companion files include Social SciSearch, Current Contents Search, and Computer & Mathematics Search.


Registry Numbers are searchable in EMBASE (BRS, Data-Star, and DIALOG), and in MEDLINE (BRS, Data-Star, DIALOG and NLM). EMBASE are mapped and searchable back to 1974. Through an exclusive arrangement with Chemical Abstracts Service RNs are searchable on BIOSIS on STN International. Search for the RN for glucose as follows:

BRS and Data-Star 50-99-7.rn. DIALOG RN=50-99-7 NLM 50-99-7 (rn)

EC codes are searchable in BIOSIS (BRS, Data-Star, and DIALOG) and in MEDLINE. Search for pyruvate oxidase as follows:

BRS and Data-Star ec adj '' (BIOSIS); ec-1-2-3-3 (MEDLINE) DIALOG ec= (BIOSIS); ec (MEDLINE) NLM ec (rn)

Enzyme and chemical names are also searchable in the RN field in MEDLINE and can be a cheap way to identify RNs:

BRS and Data-Star pyruvate-oxidase.rn. DIALOG pyruvate oxidase/id NLM pyruvate oxidase (rn)


BIOSIS is available on BRS, Data-Star, and DIALOG. The subject codes used in this database are Concept Codes (CC) and Biosystematic Codes (BC). They do not have a direct one-to-one relation with the BIOSIS keyword vocabulary.

The five-digit Concept Codes are arranged in a classified scheme and are used to describe broad subject concepts. Codes are assigned to indicate primary, secondary, and tertiary subject importance. …

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