PubMed Exercise

Open the Internet browser. Type this URL in the location or address field: http://www.ncbi.nlm.nih.gov/entrez/. The PubMed page will appear, with the query box at the top of the page.

a. Keyword search

In the query box after "Search PubMed for", enter the most important word or phrase describing your topic. For example, if you were searching for articles about the spread of the West Nile Virus in New York State and Connecticut, you could start by typing in the phrase West Nile Virus. Click on .

PubMed's Automatic Term Mapping will look for matches for your word or phrase in its MeSH (Medline Subject Headings) Index, Phrase Index, Journal Index, and Author Index, as well as keywords in article titles and abstracts. It will ignore stop words such as "about", "the", "in", so don't enter that type of word in the query box.

PubMed will then display the number of citations found, and a list of those citations. Probably there will be more citations than you wanted, and they will be not exactly about your topic, so you will probably want to search for some additional keywords. Enter another word or phrase into the query box (example: New York) and click Go. Again, PubMed will search for that entry and display citations only for that entry. If you prefer not to see a list of citations every time you enter a new term, click on Preview instead of Go.

b. Combining terms using AND, OR, NOT

Click on History under the query box. The searches you have done and the number of citations will display.

 

To combine the keyword searches, enter their numbers, preceded by a # into the query box, with a combining word, such as AND, OR, or NOT. The combining word must be in capital letters.

AND: Use AND when you want both terms to appear somewhere in each article record. Using AND will reduce the number of records found.

OR: Use OR when you want either or both of the terms to appear somewhere in each article record. It is usually used for synonyms or similar words, such as New York OR Connecticut. Using OR will increase the number of records found. When using OR, put parentheses around both terms.

NOT: Use NOT when you don't want a term to appear in an article record. Using NOT will decrease the number of records found.

Examples:

Will retrieve citations about the West Nile Virus in New York and/or Connecticut. You will get the same results by entering both terms into the query box and combining them with AND.

 

c. Using the wildcard (*)

To search for different forms of the same word, such as prevent, preventive, prevention, preventing, enter the beginning of the word, followed by an * (example: prevent*). (Caution: Using a wildcard will exclude Medline Subject Headings (MeSH)).

 

Click on Limits below the query box. The Limit menu will appear.

Click on the Languages box and select English. Click on the Human or Animal box and select Human. Try some of the other boxes if they are applicable to your topic. Click on Go in the query box, and PubMed will rerun your search using these limits for more relevant results. These limits will stay in effect for the rest of your searches as long as the check remains in the box next to Limits . Click on the check to remove these limits from your next search.

If you are getting too many irrelevant results for your search, one way to get more precise results is to choose the All Fields box, and select Title Word. Then your search will only retrieve results that have your keywords in the title of the article.

When you have entered your search and clicked on , The results will display in reverse chronological order.

The most recent articles may be labeled " [record as supplied by publisher]", and may not have MeSH terms assigned yet or abstracts available. Scroll down the list until you see a record without the label. Click on the author's name to see the abstract of the article, as well as its MeSH terms. (MeSH terms with an * are MeSH major topics).

Click on to see other citations with similar words in the title, abstract, and similar MeSH headings. Click on to see online sources of related information. If there is a box, such as above the title, that is a link to the online version of the whole journal article. Most of the online journals require a subscription, but a few may be available for free. Click on the link to see if this particular journal is free.

The Miner Library Electronic Circuit Librarian program is providing articles to you for free through the Information Access for Public Health Professionals grant until July 1, 2001 or until the budget is spent. Ordinarily, these articles would cost $11 per article.

If you see a journal article you really want to read, and it is not available online for free, click in the checkbox next to the article citation, and then click on . Follow the instructions on the Loansome Doc information sheet.

6. Clearing previous searches

Before going on to a new search, you may want to clear previous searches. Click on History under the query box to see a display of your previous searches. Click on Clear History to erase these searches.

7. Advanced Searching

a. Searching for a Medline Subject Heading (MeSH)

Medline assigns Medline Subject Headings (MeSH) to each article. For example, all articles about ways of preventing people from smoking are assigned the MeSH Major Topic "Smoking" and the subheading "prevention and control". Using MeSH ensures that you will find articles about your topic, regardless of the words the author used in the article title or abstract to describe the article.

To find a MeSH term for your topic, click on MeSH Browser on the sidebar on the PubMed page. The MeSH Browser query box will appear. Enter your keyword or phrase (example: smoking prevention) and PubMed will list the MeSH heading that is the closest match to your term, along with a definition of the subject heading and a tree of broader and narrower subject headings.

Click on Detailed Display to see a list of subheadings for the MeSH term.

In this case, the subheading "prevention and control" combined with the MeSH term "smoking" will find relevant articles. If a useful subheading for your topic exists, click on it. If you want the MeSH the topic to be the major point of the article, click on "Restrict to Major Topic headings only". Click on to choose AND, OR, or NOT to combine the MESH term with other terms in your search. Then click on to add the MeSH term to your search. To return to the PubMed search page, click on at the top of the page. Then click on History to see the results of the MeSH term search. Warning: articles published in the last month or so will not yet have MeSH terms assigned, so searching by MeSH terms won't find these articles.

b. Using the Index

When doing searches other than basic keyword searches, it is very helpful to check the Index to find out the correct entry for an author's name or a journal title or a MeSH term. Click on Preview/Index under the query box. A list of your most recent queries and the Preview/Index query box will appear.

Click on the All Fields box and choose MeSH Major Topic. Then enter your word or phrase in the query box and click on Index (example: smoking prevention). An alphabetical list of MeSH headings will appear. If you don't see your term, click on the Up or Down buttons to look for MeSH headings about your topic. The numbers in parentheses after the MeSH Major Topics are the number of citations that have that topic as the major focus of the article. If you find a useful heading, click on AND, OR, NOT to add the heading to the query box at the top of the page. Click on Go to run the search, or on Preview to add the search to your query list without getting a display of the results.

c. Searching for an author

Enter the author's last name followed by his/her inital(s) into the query box at the top of the page (example: Satcher D). If you're not sure of the author's initials, search the Index under Author Name.

d. Searching for a journal title

Enter the journal title in the query box at the top of the page, including stop words (example: American Journal of Public Health). If the journal has a title that might be confused with a keyword search, such as Nursing, search the Index under Journal Name.

8. Getting Help

Select Help from the sidebar to learn more about any function you're using.