Database Search Basics Sometimes a printed source is better. There are many sources for information. If you aren't sure where or how to find the best information, talk it over with your librarian.
There are many different databases. There are dozens of health science databases provided by the National Library of Medicine, and hundreds more databases from other vendors. Select the right database for the best information. Databases can be fulltext (such as AIDSDRUGS or CHEMID) or bibliographic (such as MEDLINE or TOXLINE). The right database may be costly; if you need a comprehensive search in a commercial database for your grant-funded research, figure those costs into the funding you ask for.
A database may be searchable through many different "search engines" or "user interfaces." The Drug Information Center uses the SilverPlatter interface for Medline searches; the Health Sciences Library has Aries Knowledge Server, the entire University may search MEDLINE and other databases through the Ovid search engine on MERLIN using a character-based interface (login as "library") or a web-based interface. There are many other web-based interfaces for Medline on the WWW of varying quality. The UMKC Clinical Medical Librarians are able to search MEDLINE using the Medlars, Ovid, Dialog, DataStar, and other interfaces as well. Your librarians can themselves be "search interfaces;" this is called a mediated search. If you don't get good search results, or if you want to be as comprehensive as possible, consider asking your librarian or another experienced searcher to try, then compare your results and the search strategies you used.
Information is quicker and easier to find now than ever before, but it still takes time and persistence. Try to allow enough time, and don't give up too easily.
THESAURUS Many databases contain information that is indexed to subject terms from a controlled vocabulary, or thesaurus. MEDLINE uses MeSH, or Medical Subject Headings. For best results in a subject search, use terms from the database thesaurus whenever possible. The alternative is to use words you expect to find in the text of the entries in a database, called textword searching. In MEDLINE, a textword search looks for a word in the title or abstract of a journal article citation. A textword search will only retrieve citations to articles in which the authors used the same language as your textword. For example, if you search for NIDDM, only articles with NIDDM in the title or abstract will be retrieved. If you search for the MeSH term diabetes mellitus, non-insulin-dependent you will retrieve all articles on this subject, even if the author used the term NIDDM or Type II diabetes. The best search strategy may involve both textword and thesaurus terms. The search terms you choose will be the most important, and often the most difficult, aspect of your search.
FIELDS You may search particular fields of a database entry, such as title field, author, name of substance, publication type, registry number, product code, country code, etc.
LIMITERS It is possible to limit your search. Generally, you will have searched for a subject (e.g., hypertension) or combination of subjects (e.g., thrombolytic therapy and myocardial infarction) and retrieved a large set of citations. In MEDLINE you may then limit your search to a range of years, to a publication type such as REVIEW or GUIDELINE or CONTROLLED TRIAL, to studies including a particular sex, to animal studies, to a particular language, etc. You may also limit your search to a journal subset, such as Abridged Index Medicus, or Nursing, or Dental.
TRUNCATION Many databases allow truncation to retrieve variant spellings of a textword or name. The truncation symbol depends on the user interface. Be sure to use as much of the word as you are sure of. "Com$" as a textword will retrieve communicate, communicable, computer, compare, and a zillion other words. "Compute$" will retrieve compute, computer, computed, computers, but not computations. Internal truncation symbols can allow for one extra or one different letter within a word. "Anders#n" as a name retrieves Andersen or Anderson. This is useful for textword searches in British or American literature: "hypophosphat#emia" or "tum#or;" or for unusual plural forms: "wom#n."
ADJACENCY SEARCHING Many databases allow textwords to be searched together as phrases with an adjacency command. This is useful for phrases which have come into vogue but have not yet been accepted as part of the indexersÕ controlled vocabulary.
EXPLODE Because MeSH is a hierarchical subject vocabulary, terms have narrower and/or broader subject headings. Articles are indexed to the most specific subject headings which apply to their content, so a search for "nose," for example, will not retrieve articles exclusively about the nasal bone, or the nasal septum, or the nasal mucosa. To retrieve articles about the nose or any of its specific structures, use the explode command: "EXP nose." This command can be extremely useful in MEDLINE searches.
SEARCH LOGIC (BOOLEAN CONNECTORS) Database searching is particularly useful when you want to combine two or more subject concepts in your search. For example, if you are interested in SLE and pregnancy, a search of SLE would yield many citations that did not mention pregnancy, and a search of pregnancy would yield many citations that did not concern SLE. A search of "lupus erythematosus, systemic AND pregnancy" will yield only those citations to articles in which both SLE and pregnancy are discussed. AND always shrinks your pool of citations; the articles you retrieve must contain your first subject and your second subject and your third subject, etc. OR widens your pool of citations; you will retrieve articles about your first subject or your second subject or your third subject, etc. For example: "kidney OR glomerul$ OR nephr$ OR pyel$ OR renal;" "JAMA OR N ENGL J MED." NOT should be used with caution, but can be useful. If you wish to search for articles about uses for allopurinol other than gout, you can search "allopurinol NOT gout." You will exclude articles about gout, but will possibly miss a good article that reviews all the therapeutic uses of allopurinol, including gout.
SEARCH TOOLS For the best search results, use the best search terms. Many databases publish a thesaurus, tree, and/or permuted index, as printed volumes or as files attached to the search engine. For example, if you find it difficult to determine the best MeSH terms for your search, there are several search tools which can help you. Annotated MeSH lists all the MeSH terms alphabetically, and will tell you the scope of a term and the date it was added to the thesaurus. Permuted MeSH maps each word in a MeSH term to the terms that employ that word. A search for "failure" or "heart" or "congestive" will all lead to the MeSH term "heart failure, congestive." A search for "staging" will lead you to the MeSH term "neoplasm staging." Tree Structures will show the hierarchical relationship among terms, and brings together related terms that do not appear together alphabetically, such as terms for statistical concepts. Supplementary Chemical Records lists more than 20,000 chemical names, with their trade names and registry numbers, and refers you to the MeSH terms under which those chemicals are indexed.
Too many "hits." If your search retrieves too many citations, you might try searching a narrower or more specific term. You might choose to make your most important term the focus (or main concept) of the articles you seek. You might limit your retrieval to English, or human, or to Abridged Index Medicus (which includes journals the UMKC Health Sciences Library is most likely to have on hand), or to a particular age group. You might attach a subheading to a term. For example, the search statement fluoxetine/ae,po,to searches for adverse effects, poisoning, or toxicity of fluoxetine.
Too few "hits." If your search retrieves few citations (or none), consider using the explode command, or using a broader term with the explode command. If you have ANDed several terms together, try removing the least important or most specific terms. If you have focused your search on one or more terms as major descriptors, try removing the focus and run the search again. Try removing one or more of your limiters or subheadings. (Except in marketing or business databases, use the generic rather than the trade name of a drug. With new drugs, try searching by every form of its name, including registry numbers.)
Textword to controlled vocabulary. If you can't find a good controlled vocabulary term to search, use a textword. Browse the citations you retrieve until you find a title that looks like the kind of article you want, and look at the subject terms attached to it. Then run the search using the most significant subject terms for that article that fit your search interest, to find additional articles.
The success of any database search can depend on the structure of the database itself, the nature of the search question, the quality of the search engine, and the skill of the searcher. If you are not satisfied with the results of your search, consult with your librarian, who may offer different skills or new search strategies, or may have access to different databases and better search engines.