CALDER OVID MANUAL
WWW
MEDLINE TUTORIAL
Louis Calder Memorial Library - University of Miami School of Medicine
http://calder.med.miami.edu
- From our homepage, http://calder.med.miami.edu, click on "MEDLINE" (under the "Quick Links" menu on the left).
- Click on "I.P. (Internet Protocol)" or "Password." The password option will allow you to save your search; use this option if you are concerned about timing out and wish to recover your session or if you plan on continuing the same search at a later date. If you are a UM/JMH student, faculty, or staff member, call the Systems Department (305-243-5530) to request a user ID and password application.
- After you log in, a list of all available databases will appear, from which you will be prompted to choose one to search.
- Click directly on the desired database name to begin.
- If you need more information, click the "i" icon to the left of any database name to display its field guide. The field guides include sample records, a list of searchable fields, and producer information. If you click "i," you will need to click your web browser's "Back" button to return to the database list.
3. Define Your Search Topic and Concepts
This is a preparatory step and not part of the database. Analyze your search needs and define your search topic in your own words. State the topic in a well-focused sentence or question. Example: What is the risk of breast cancer for women taking combination hormone replacement therapy? By defining your specific information needs, searching will be accurate and relevant. The next step is to underline the search terms, such as the patient or subject group, problem, intervention, outcome, and/or type of study that will provide the best information. Example: risk, breast cancer, women, hormone therapy.
- Enter each key term to be ANDed along the top section of the grid (risk, breast cancer, women, hormone replacement therapy).
- Underneath your key terms, write down any possible search terms and synonyms for each concept (risk: probability, chances; breast cancer: breast neoplasms, breast tumors; women: female, human; hormone replacement therapy: estrogen replacement therapy, estrogen/progestogen, estradiol/progestin, estrogen/progesterone).
- Select some or all of the synonyms to be ORed and place each in their respective column under the OR sections (not shown).
- Below the grid, write down the steps in which you want to search the terms. Put in the AND/OR combinations. Remember to include any limits such as age groups, language, year(s) of publication, etc. Sample abbreviated strategy:
- hormone replacement therapy
- estrogen replacement therapy
- 1 or 2
- breast neoplasms
- 3 and 4
- risk
- 5 and 6
- limit 7 to human, female,
and English
- Use the command line box located under "Enter Keyword or phrase" in the middle of the "Main Search Page." Click inside the command line box and type your first concept term. Note: the Ovid databases are not case-sensitive; therefore, you do not need to capitalize terms. Then click on the "Perform Search" button to be taken to the "Mapping Display" screen.
- Do not enter more than one key concept at a time or extraneous phrases. Entering one concept at a time will enable you to take full advantage of the mapping feature (which suggests related terms) and will display the total number of citations of each concept.
- If the "Map Term to Subject Heading" box is checked, the system will attempt to translate the term to the appropriate Medical Subject Heading (MeSH) term. If the system does not map your concept to an exact match or to a closely-related MeSH term, select near the bottom of the screen "search as Keyword" to search the concept as a word in the Title, Abstract, Subject Heading, or Registry Number Word (screen shot shown on next page.) Searching via keyword does not find articles based on relevance but locates articles that possess the keyword. The prompt indicates what type of query Ovid currently expects, e.g., "keyword." You may also use Ovid command line syntax (see step 12 for information on using these abbreviation shortcuts).
- If you wish to search other fields, such as Author, Journal, Title, and keywords in various fields (Abstract, Institution, etc.), you must first click on the appropriate icon at the top of the "Main Search Page" and then enter the term in the command line box.
- A keyword search will look for the occurrence of the exact word or phrase within Titles, Abstracts, Registry Number Words, and Subject Headings, but there is no guarantee that the word or phrase will be the topic of the article.
- On the "Main Search Page," disable the "Map Term to Subject Heading" checkbox (uncheck it), type in your term(s) to be searched, and click on the "Perform Search" button. (In this example, the term was "Spinal.")
The example above shows a search for one keyword. Use the adjacency operator (adj) to retrieve two or more query terms within a number (n) of words of each other and in any order. The number n should immediately follow adj without a space, as in physician adj5 relationship. This search will retrieve the words physician and relationship within 5 words of each other in either direction.
6. Map Term to Subject Heading
The "Map Term to Subject Heading" checkbox activates the Ovid mapping feature. When you type your query at the "Main Search Page" and click the "Perform Search" button, you will have the opportunity to select the Medical Subject Headings (MeSH) or controlled vocabulary term(s) that most closely matches your desired concept. Ovid automatically checks the "Tree" for the most appropriate terms and displays those terms in a list. You will also have the opportunity to choose subheadings.
- The checkbox preceding "Map Term to Subject Heading" is enabled by default; to disable this feature and do a keyword search, uncheck the box.
- Enter a single concept to search in the command line box.
- Click the "Perform Search" button.
- The "Mapping Display" screen (shown next page) lists possible relevant MeSH terms.
- Click any hyperlinked term to see its "Tree." If there is a plus sign before the term it means there are additional MeSH indexed under it. Click on the plus sign to see the narrower terms. Use your browser's "Back" button to go back to the "Mapping Display" screen.
- Click the "Select" checkbox to the left of desired term(s). If none of the terms appears to match your desired subject, click the checkbox for the last line, "search as Keyword."
- Using the pull-down menu at the top of the page, combine your selections with the Boolean OR (to retrieve at least one selected term in each document) or AND (to retrieve all selected terms in each document).
- Clicking the "Explode" checkbox(es) for any term(s) will search the term(s) ORed with all its conceptually-narrower terms. Choose "Explode" for the most comprehensive retrieval. For example, exploding "Hormone Replacement Therapy" includes "Estrogen Replacement Therapy" as well as "Hormone Replacement Therapy" since "Estrogen Replacement Therapy" is a subset term in the database.
- Clicking the "Focus" checkbox(es) will specify whether the chosen term should be one of the main topics discussed in the retrieved documents.
- Clicking on both the "Explode" and "Focus" checkboxes will retrieve articles in which any of the terms (the broad MeSH term or its conceptually-narrower terms) will be a main topic of the article.
- Click the "Continue" button to move to the next step. Or, click the "Main Search Page" button to cancel the mapping process.
7. Medical Subject Headings (MeSH)
The MEDLINE database is indexed by professional reviewers who read each article completely and then assign index terms to describe (as specifically as possible) the contents of the article. The terms come from a standardized list of vocabulary terms and definitions called MeSH (Medical Subject Headings). The idea behind MeSH is that all articles about the same concept are assigned the same standard subject heading, regardless of the exact words the author uses. For example, one author may use shingles, the other herpes zoster, but both articles will be indexed to herpes zoster. The best way to search MEDLINE is to use the MeSH terms.
When you click the "Author" icon to search for documents written by a certain person, the phrase above the command line box changes to "Enter the Author's last name, a space, and first initial if known." Anything typed at the author prompt will be searched only in the Author (au) field of the database. The Ovid databases are not case-sensitive; therefore, you do not need to capitalize terms or names.
- Enter a last name, followed by a space and the first and middle initial(s), if known. Example: Banovac K.
- In the resulting "Authors Index Display," you can use the on-screen buttons to page forward and backward to view index entries. It is important to scan the index for name variations. Authors sometimes publish with and without their middle initials, so the same author may be entered under more than one name form. Click in each name's checkbox that might be relevant and then click on the "Perform Search" button. The system will OR together all name variations and post the results at the "Main Search Page" in the "Search History" window.
When you click the "Title" icon on the "Main Search Page," you can search for articles that contain your desired word or phrase in the Title field. Note that the "Main Search Page" command line prompt has changed to "Enter a word or phrase to be searched in the title." Anything typed at the title prompt will be searched only in the Title (ti) field of the database.
- Enter the word or phrase to be searched.
- If you wish, select any desired limits on this page.
- Then click the "Perform Search" button.
- The search results will be posted at the "Main Search Page" in the "Search History" window.
When you click the "Journal" icon on the "Main Search Page," you can search for articles that appeared in a desired journal. Note that the "Main Search Page" command line prompt has changed to reflect a journal search. Anything typed at the journal prompt will be searched only in the Journal (jn) field of the database.
- Enter the first few complete words (no abbreviations) of the journal title (omit initial articles such as "the"). For example, the title "The Journal of Clinical Investigation" should be entered as "Journal of Clinical Investigation." The Ovid databases are not case-sensitive; therefore, you do not need to capitalize terms. Note that a few journals are searched by their acronym, such as "JAMA" instead of the "Journal of the American Medical Association."
- From the resulting "Journal Index Display," click the checkbox next to the desired journal name, and then click the "Perform Search" button.
- The search results will be posted at the "Main Search Page" in the "Search History" window.
Truncation is used to ensure retrieval of all possible variations of a term.
- The "Map Term to Subject Heading" option needs to be deselected (uncheck it).
- Enter common word stems by ending them with the character $. For example, entering hypno$ would retrieve hypnotize, hypnotized, hypnotizing, hypnosis, hypnotics, etc. from Titles, Abstracts, Registry Number Words, and Subject Headings.
- There are additional truncation options which are linked from the "Help" button. (From "Help," click on the "Command Line Syntax and Advanced Searching Techniques" hyperlink, and then click on the "Truncation and Wildcards" hyperlink.)
Many Ovid commands may be entered directly in the command line box. This lets advanced users bypass the icons displayed at the top of the "Main Search Page" to save time. The list below explains the most frequently-used commands. You may use uppercase or lowercase letters. Be sure to observe the correct number of periods and their placement. Consult the "Database Field Guides" for more information (from the "Choose a Database" screen, click on the "i" icon in front of each database to access the field guide OR from the "Main Search Page," click on the "Help" button and then on the "Command Line Syntax and Advanced Searching Techniques" hyperlink):
| .au. Searches by author smith j.au. (authors with "smith"
as a last name abd first initial "j") |
.jn. Searches for keywords in the journal name jama.jn. |
.fs. Acts as a floating subheading; searches for subheadings attached to any MeSH term ci.fs. |
| .mp. Searches for keyword(s) in the following fields: Title, Abstract, Subject Heading, and Registry Number Word spinal.mp. |
.in. Searches for keywords in the institution name jackson memorial hospital.in. |
..ps Displays your search
history without the article citations; if desired, use your Web
browser's print function and print your search strategy |
| .ti. Searches for keyword(s) in the title only diabetes after pregnancy.ti. |
.ab,ti. You can search in more than one field at a time; this example searches for keyword(s) in the abstract or title breast cancer.ab,ti. |
..o Ends your search session
and returns to the login page |
| .ab. Searches for keyword(s) in the abstract only double-blind.ab. |
.yr. Searches within a specified year or year range 1999-2001.yr. |
..pg(x) Deletes sets in the "Search History" window; (x)=line number in search history, do not use parentheses ..pg2-3 (purges search sets 2
and 3) |
- Search for a word or phrase contained in one or more specific fields by clicking on the "Search Fields" icon at the top of the "Main Search Page." Enter a word or phrase and select the desired field (Title, Institution, CAS Registry Number, Publication Type, Volume Number, Page Number, etc.).
- For example, you may want to locate articles by authors who are affiliated with institutions that specialize in the treatment or research of headache. From the "Search Fields/Indexes" screen, select "Institution" from the list of options and type "headache" in the command line box. If you wish to see other institutions with similar names, click on the "Display Index(es)" button, click in the checkboxes of desired institutions, and then click on the "Perform Search" button.
- Searching additional fields can be especially useful in locating documents when you have an incomplete citation. You can, for instance, find an article if you know a few words from the journal title, year, and volume number, whether or not you remember the names of the authors or title of the article. You will find this feature especially useful to verify article citations.
"Search Fields/Indexes" screen:
The "Search History" window shows the last four sets you have created. When you click the "Perform Search" button on the "Main Search Page," results appear immediately, usually in groups of 10 article citations at a time. The "Titles" display begins immediately below the search interface, and you can scroll down to see it. The "Titles" display starts with a section heading that contains the results of your search, the number of citations retrieved, and the range of currently-displayed items (e.g., 1-10, 11-20, etc.) Several or all of the following links appear at the end of each citation, allowing you to display more information:
- Abstract--summary of the article.
- Complete Reference--includes Numeric Identifiers, Author, Title, NLM Journal Code, Comments, Source Journal Subset, Local Messages, Country of Publication, MeSH terms, Registry Numbers, ISSN, Publication Type, Language, and Entry Month.
- If only Abstract and Complete Reference options are given, choose Complete Reference, since it will display the abstract as well as the MeSH terms. After viewing the complete reference, you may identify other MeSH terms to be incorporated into your search. Click directly on the desired MeSH term and it will be added to the "Search History" window for further use.
- Ovid Full Text--links to the full text in both HTML and/or PDF format via Ovid. Click on the full text link. Once the article opens, scroll down and click on the PDF option.
- Full Text—connects to the publisher or aggregator site for the HTML and/or PDF format of the article. If available, select the PDF option.
- Library Holdings--connects to the UM Calder Library online catalog, CALLCAT, and lists whether or not the library owns the journal in either print and/or electronic format.
- Buy Now—links to Ovid’s Pay Per View where you may purchase immediate access to some full text articles in journals not held by Calder Library. If available, use Calder’s Interlibrary Loan service which is much more economical.
"Titles" display screen:
If you would like to view only selected articles, click in the checkbox to the left of the desired articles. Ovid will retain your selections, so you can use the "Previous Citation(s)" and "Next Citation(s)" buttons to navigate page-by-page through the "Titles" display. When finished, click on the "Main Search Page" button. Your chosen citations will appear as a separate set in the "Search History" window. Later, you could choose to print, email, or save (to floppy diskette) those citations.
Every time you click the "Perform Search" button, Ovid keeps a record of your search in the "Search History" window. Each search (also known as a set) is numbered consecutively in the "#" column. The number of documents retrieved by each search is listed in the "Results" column. Once you have created a search, a new column appears, called "Display." Click the "Display" link to view the results of any search. Via the command line box, you can refer to any search in a new query by typing its set number.
16. Expand/Contract Search History
The "Search History" window shows your last four searches by default. If you have performed more than four searches in your current session, click the "Expand" search history button to view them all. The "Expand" button will then change to the "Contract" search history button. If you decide to display only the last four searches, click on the "Contract" search history button.
17. Saving and Retrieving Searches, Copying Searches and AutoAlerts (SDIs)
- If you have created any searches during your current session, a new button will appear, "Save Search History," that lets you save your searches on the server so that you can return to them later. After clicking on "Save Search History," follow the prompts and click on the "Save Search" button. (If you logged in without a password, you can only save your search temporarily to the server.)
- You can run a previously-created saved search by clicking on the "Saved Searches" button. Select the checkbox by your saved search, click on the "Run Search" button, and then click on the "Main Search Page" button. Your search will be displayed in whichever Ovid database you currently have open--even if it's a different database. Therefore, if you saved your search in MEDLINE, make sure you are in the MEDLINE database and not in another database before running your saved search. Note: any active searches must be deleted first, otherwise, a saved search will be added to that search in the "Search History" window.
- If your search session timed-out, see step 35, Timeout and Session Recovery for further instructions.
- In the "Results Manager," you can save your article citations to a floppy diskette for printing later. Note: this option does not allow you to re-run your search on MEDLINE.
- AutoAlerts (SDIs) are searches which are saved permanently for a particular database and are executed whenever the specified database is updated. When they are executed, new article citations which match your search criteria are emailed to you. This saves you time if you want to know if new articles were written on your chosen topic. Note: this feature is only available to UM/JMH students, faculty, or staff members; to access this feature, you must initially log in with your UM/JMH user ID and password (choose the "Password" option), perform your search (or re-run it if previously-saved), click on the "Save Search History" option, and then follow the prompts.
You can delete selected sets in the "Search History" window or delete the search entirely.
- Click on the "Delete Searches" button. On the "Delete Searches" screen, don't forget to click on the "Expand" button to see the complete search history. Click in the "Delete All Searches" checkbox or click on the checkbox(es) of the set(s) you want to selectively delete. Note: you may be given a warning if your selection(s) have dependent sets. Then click on the "Continue" button.
"Delete Searches" screen:
Find everything about the topic (may include some irrelevant items). In a broad search, use fewer key concepts or search statements to increase the number of article hits.
- Search for terms in multiple fields.
- Combine related terms with OR.
- Use the "Explode" button.
- Do not restrict to "Focus."
- Do not attach subheadings or floating subheadings.
- Do not apply limits.
"A" or "B"
Find a few good references on the topic (may miss some relevant items). In a narrow search, use more key concepts and complex search statements to retrieve fewer articles. Search results are often further restricted by applying limits such as age groups, gender, language, publication types, etc.
- Restrict to "Focus."
- Attach subheadings or floating subheadings, if appropriate.
- Combine sets with AND or NOT.
- Apply limits.
- Evaluate a few good documents and narrow your search by adding the MeSH terms found in the relevant records.
"A" and "B"
"A" not "B"
Click the "Tools" icon at the top of the "Main Search Page" to activate the special searching capabilities of this database, including Medical Subject Headings (MeSH). Tools include the "Tree," "Permuted Index," "Scope Note," "Explode," and "Subheadings." On this page, click the button for the tool you wish to use, enter the desired keyword, and click the "Perform Search" button. Because they are designed according to the database structure, "Tools" can be used to learn more about database design and for shortcuts to certain structural elements in the database. Note: the "Tools" feature is not available in every database.
"Select a Tool to View" screen:
In databases such as MEDLINE, CINAHL, etc., index terms are arranged in a hierarchy, with broader concepts such as "Wounds and Injuries" near the top, and more specific terms like "Spinal Cord Injuries" near the bottom. The hierarchy of terms is known as a "Tree." You can browse through as much of the "Tree" as you wish, looking for terms to add to your search.
- Click on the "Tools" icon on the "Main Search Page," select "Tree," type in your MeSH term or MeSH phrase, and click on the "Perform Search" button. You will then be taken to the "Tree" display page. (You can also access a MeSH term's tree and its "Contexts" feature by clicking on the term from the "Mapping Display" page. See step 6 for details.)
"Tree" display screen:
The same MeSH term may appear in different contexts. To view all occurrences of your term, click on the "Contexts" button. From there, you may find other terms to search. Note: your MEDLINE search will retrieve all occurrences of your MeSH term, even if it is in different trees. You can make your selections from this screen or use your browser's "Back" button (or click on the "Full Tree" button) and make your selections from the "Tree" display screen.
"Contexts" display screen:
The "Permuted Index" does a keyword search for Medical Subject Headings (MeSH). Use this feature to learn of MeSH related to your subject. Note: the "Permuted Index" will allow you to search with a single term only. For example, searching with the term "Spinal" will locate all MeSH containing it, such as "Spinal Cord Neoplasms, " "Anterior Spinal Artery Syndrome, " and "Spinal Cord Injuries. "
- From the "Main Search Page," click on the "Tools" icon.
"Select a Tool to View" screen:
- Type ONE TERM only in the command line box.
- Choose "Permuted Index" and click on the "Perform Search" button.
- If the "Permuted Index" results display is more than one page, you can go forward and backward through the list by clicking on the red double arrows marked "[Forward in List]" or "[Back up in List]."
- You can select your MeSH
term(s) from the results display and then click on the "Continue"
button to perform your MEDLINE search. Or, you can click on the "Main
Search Page" icon to exit the "Permuted Index."
A "Scope Note" contains information about the use of a MeSH term. This information may be a simple definition of the term, or it may consist of very detailed instructions to the searcher on how to apply the term. Some of the details may be in a form that is not easily understood by a non-indexer, but often there is very useful information that can be found by scanning a lengthy "Scope Note."
- Because the standardized MeSH terms are arranged in hierarchical "Trees" and articles are indexed with only the most specific headings, a very powerful type of searching, called exploding, is possible. Using the broad MeSH term "Spinal Cord Injuries," for example, would not necessarily retrieve articles indexed with the narrower term "Central Cord Syndrome," unless you "Explode" the term "Spinal Cord Injuries."
- If a suitable term appears on the "Mapping Display" screen, click on that term to view its "Tree." This will show you how your term is related to similar terms, which are broader or narrower than yours. If all of the narrower terms are of interest to you, click in the "Explode" checkbox to the right of the broadest term in the list. (Click on the letter "i" to read a "Scope Note" definition of a subject heading.) If only the specific term is useful, click in the "Select" checkbox to the left of that term.
- Example: "Spinal Cord Injuries" is the broad term. "Central Cord Syndrome" is a specific term for a type of spinal cord injury. Exploding "Spinal Cord Injuries" will search for "Spinal Cord Injuries," as well as all the other more specific term(s) indented below it, ("Central Cord Syndrome").
- Articles are indexed in MEDLINE using the most specific MeSH term available, so it is very important to select the correct level of specificity. If you want articles about "Spinal Cord Injuries," you would miss many of them by selecting only the narrower term "Central Cord Syndrome." To avoid losing relevant citations, it is often best to search all of the terms in its "Tree." Clicking in the "Spinal Cord Injuries" checkbox and clicking in the "Explode" checkbox will instruct the system to OR together the broader heading with all of the narrower terms indented under it. (Go to step 22, "Trees" for further information.) Click on the "Continue" button to go to the next search step, choosing a subheading.
If you wish to only retrieve articles where the MeSH term you selected is the major subject being discussed, click in the "Focus" checkbox to the right of the term. However, this is not recommended for most searches unless the amount retrieved will likely be very large. Click on the "Continue" button to proceed to the next search step, choosing a subheading.
27. Explode and Focus Simultaneously
You can explode and focus. For example, exploding "Spinal Cord Injuries" will also retrieve "Central Cord Syndrome." If you also clicked "Focus", you would retrieve articles in which either or both term(s) is/are the major subject(s) of the article.
Databases indexed with MeSH headings have a list of qualifiers, called subheadings, which can be used to fine-tune or narrow a search. Subheadings tend to be general concepts such as "etiology" or "toxicology," which, when linked to MeSH terms, give a very specific idea of what an article is about. For example, an article about "the medical complications of spinal cord injuries" would be assigned the MeSH term "Spinal Cord Injuries" and the subheading "complications." In the document, the MeSH term and subheading would display together, separated by a slash: "Spinal Cord Injuries/co [Complications]."
- Click on the letter "i" to the left of any subheading to see its definition; use your browser's "Back" button to return.
- Select one or more subheadings using the checkbox, or click the "Include All Subheadings" checkbox for maximum retrieval.
- Using the pull-down menu at the top of the page, combine your subheading selections with Boolean OR (to retrieve at least one of the individual terms in each document) or AND (to retrieval all in each document).
- Click the "Continue" button to perform your search and return to the "Main Search Page."
| ADVERSE EFFECTS ae adverse effects |
ANATOMY & HISTOLOGY ab abnormalities |
ANALYSIS an analysis |
| CHEMISTRY aa analogs & derivatives
|
COMPLICATIONS co complications |
CYTOLOGY cy cytology |
| DIAGNOSIS di diagnosis |
EMBRYOLOGY em embryology |
EPIDEMIOLOGY ep epidemiology |
| ETIOLOGY ci chemically induced
|
METABOLISM bi biosynthesis |
ORGANIZATION & ADMINISTRATION ec economics |
| PHARMACOLOGY ad administration &
dosage |
PHYSIOLOGY bi biosynthesis |
STATISTICS & NUMERICAL DATA eh ethnology |
| SURGERY su surgery |
THERAPY dh diet therapy |
THERAPEUTIC USE ad administration &
dosage |
Use floating subheadings when you wish to retrieve articles about that subheading. For example, to indirectly answer the question, "what parts of the body does smoking affect?" combine the MeSH term and subheading, "Smoking/ae [Adverse Effects]," with the floating subheadings "etiology (et)" or "chemically-induced (ci)." Thus, you would retrieve articles on various diseases (such as peptic ulcers, neoplasms, and osteoporosis) that were caused by smoking. As you can see, floating subheadings will attach to any MeSH term, so you may retrieve some irrelevant articles.
- In the command line box on the "Main Search Page," type the two-letter subheading abbreviation and ".fs." After clicking on the "Perform Search" button, combine the floating subheading(s) with your MeSH term(s) in the search history.
Like MeSH terms, you can explode floating subheadings. Exploding the subheading "statistics and numerical data (sn)" would include all of its related subheadings, "ethnology (eh), "epidemiology (ep)," and "mortality (mo)." Instead of typing those terms separately as floating subheadings, you can type "sn.xs." in the command line box on the "Main Search Page." Note that the floating subheadings will be attached to at least one MeSH term used to describe the article. They will not necessarily be attached to the particular subject heading you used in your search. Therefore, you may retrieve some articles irrelevant to your search.
- In the command line box on the "Main Search Page," type the two-letter subheading abbreviation and ".xs." After clicking on the "Perform Search" button, combine sets in the search history.
See the chart in step 28, Subheadings, for the categories and contents for each of the 20 exploded subheadings. Each entry is preceded by its two-character abbreviation. The first heading listed defines the category.
When you click the "Combine" icon on the "Main Search Page," you can create a new search set that represents the intersection (AND) or union (OR) of two or more of the previously-created sets. You must have at least two sets in your search history to use the "Combine" feature. Combining the key concepts in your search topic with the Boolean connectors OR or AND enables you to formulate your search statement in language that will be interpreted by the system as follows. OR retrieves documents that discuss either concept, and is used to connect synonyms or related concepts and to increase retrieval. AND retrieves documents that discuss both concepts and is used to restrict retrieval.
- On the "Main Search Page," click on the "Combine" icon.
- Click the checkboxes under the "Select" heading that represent the sets you want to combine. You must click at least two checkboxes.
- Choose OR or AND from the "combine selections with" drop-box. By combining two or more sets using OR, a new set will be created which contains all the documents in all the selected sets (with duplicates eliminated). This is also known as the union of the sets. By combining two or more sets using AND, a new set will be created which contains only those documents that the selected sets had in common (with duplicates eliminated). This is also known as the intersection of the sets.
- Click the "Continue" button to perform the function you have selected and return to the "Main Search Page." If you would like to cancel your combine request, click the "Main Search Page" button.
- If you have formed two or more sets, you can enter your combine command directly in the command line box on the "Main Search Page."
For example, if you would like to combine sets #1 and #2, you can use the AND, OR, or NOT operators. Your statement will be processed from left to right, unless you specify another order via parentheses. Examples:
- 1 and 2 and 3
- 1 not 4
- 1 and (2 or 3)
- 4 not (dogs or cats)
- (birds and bees) or (dogs and cats)
- (Spinal Fractures or Spinal Cord Injuries) and Intratracheal Intubation
Note: items in parenthesis are processed first and capitalization is not required.
- You can change databases to start a new search or re-run the same search strategy in one or more databases. After completing your initial search, click on the "Change Database" icon at the top of the "Main Search Page."
- From the "Choose a Database" page, click on the database you wish to search. You can search up to five databases simultaneously by clicking on the tab at the top of the screen, "Select more than one database to search," clicking in the checkbox to the left of the desired databases, and then clicking on the green vertical band, "click to begin search." Simultaneously-searching multiple databases tends to give inconsistent results because some databases (like CINAHL) do not consistently use MeSH terms; thus, it's usually best to search each database individually so it can prompt you to use an alternate term.
- If you have already created searches and want to transfer them to the new database without having to retype them, click on the "Open and Re-Execute" button at the "Change Database" screen. Remember: every database is different, so a search in one database may need to be modified to work well in another database. Therefore, it's usually best to choose the "Open and Clear History" option and retype your search.
"Choose a Database" screen:
"Change Database" screen:
You can limit your search statement prior to clicking on the "Perform Search" button by selecting one of more of the following limits:
Human: articles which are primarily about human subjects. It will retain articles about both human and animal subjects. If you limit by Age Group you do not need to use this limit.
English Language: articles which are written in the English language. Foreign language articles with English abstracts will be eliminated.
Review Articles: articles which are reviews of a subject. Includes all review types: Review Literature; Review of Reported Cases; Review, Academic; Review, Multicase; and Review, Tutorial.
Abstracts: restricts retrieval to documents which include an abstract. All abstracts included in MEDLINE are in English and were written by the author(s) of the original article. Will include foreign language articles with English abstracts.
EBM Reviews: articles or studies that have been included by the Cochrane Collaboration when creating a Topic Review or articles that have been reviewed in the ACP Journal Club or BMJ Evidence-Based Medicine publications or in the Database of Abstracts of Reviews of Effectiveness (DARE). By their inclusion in these publications, these studies have met strict Evidence-Based Medicine criteria.
Latest Update: articles which were most recently added to the database.
AIDS, Bioethics, Cancer, Complementary Medicine, History of Medicine, Space Life Sciences, Systematic Reviews, or Toxicology: restricts retrieval to these areas.
Publication Year: restricts retrieval to any of the years covered by this segment of MEDLINE.
- To limit previously-created sets in the "Search History" window, click the "Limit" button, select the search set, and follow the instructions on your screen. You can limit your search results by variables such as gender, age, year(s) of publication, publication type, language, etc. Follow the online instructions to select more than one choice within the same drop-box.
- The "Search History" window is replicated at the top of the "Limit a Search" page. Make sure the set you want to limit is selected. Click one or more limits, and click the "Limit Search" button. If you apply one limit at a time, beginning with the most important one, you can later add more limits to retrieve fewer articles.
"Limit a Search" screen:
33. Filtering for Evidence-Based Medicine (EBM)
To identify the top-level, best-available research articles for clinical decision-making and practice, filter your retrieval for original articles that are evidence-based, and not just opinion papers, case reports, or secondary review papers. This filtering is done by narrowing your retrieval to the Medical Subject Headings (MeSH) or publication types listed at the end of this section. Some of the terms and types are appropriate when searching for evidence-based articles on therapy-related topics. Others should be used when searching for evidence-based articles on diagnostic tests and procedures, etiology, or prognosis.
You can also limit your search to "EBM Reviews" by clicking in the checkbox located under the command line box, or by clicking on the "Limit" icon and then in the checkbox for "Evidence Based Medicine Reviews." (Note: there are other article reviews options from "Limit a Search" screen. Click on the "i" to the left of the checkbox to read the scope of each.) When you limit your search to the "EBM Reviews" you will get the highest-quality review articles, but perhaps very few or not on every topic. Using the filters described below will net you more EBM articles.
Searching with a group of specific MeSH terms and unique keywords can act as a filter or hedge to find the best articles for answering a clinical problem. The better articles would be those whose results are based on scientific evidence. After setting up a filter for either "therapy," "diagnosis," "etiology," or "prognosis," a search can be added in MEDLINE to sift through the list and retrieve the evidence-based articles. Individual filters can be saved on Ovid as permanently-saved searches for further use. The following examples are largely based on searches developed by Ann McKibbon and Cindy Walker-Dilks of McMaster University in Hamilton, Ontario, Canada.
