Finding the Evidence: Evidence-Based Searching Methods

Example 1: Diabetes & Hypertension

Findings after obtaining a history and conducting physical exam

A 39-year-old man without previous chest discomfort comes to the emergency department after work. Early that day he had felt unwell and nauseated; he had had a vague sensation of chest discomfort and had begun to sweat profusely. The unpleasant experience lasted for about 2 hours, after which the patient felt tired but otherwise normal. At the end of his work day, feeling rather nervous about the episode, he came to the emergency department. The patient has no family history of coronary artery disease. He has had hypertension for 5 years that is controlled with thiazide, has a 15-pack-year smoking history, and has a normal lipid profile. His physical examination, EKG, creatine kinase level, and troponin I level are all normal.

Population

Hypertensive type 2 diabetic patients without diabetic complications

Young men with atypical symptoms and normal EKG and cardiac enzymes presenting with possible unstable angina

Outcomes

Severe angina, myocardial infarction, heart failure, or arrhythmia, all within the next 72 hours

MUSC ONLY

Your search results will be more relevant if you track your topics to the appropriate MeSH (Medical Subject Heading). Be specific, selecting the narrowest term that fits the clinical question. Go into the subject tree, when necessary, by clicking on the term itself. Examples: Diabetes; Angina

"Explode" means to include more specific subjects related to your chosen topic. For example, exploding "diabetes mellitus" in MEDLINE will not only get articles on the general topic of diabetes mellitus (62,702 articles), but also articles on the more specific subjects of diabetes mellitus type 1, diabetes mellitus type 2, gestational diabetes, obesity in diabetes, etc. (173,722 articles).

With EBM searching, it is important to choose the most specific term relevant for your query. To view the narrow terms included when exploding, click on the subject term itself to explore all the narrower terms, and the related terms around it in the subject hierarchy. For Example 1 (above), it would be best to choose the specific subject "Diabetes Mellitus, type 2"

It is often helpful to focus your most important concept in EBM searching.

Checking the "Focus" box makes sure your subject is one of the major points of the article. MEDLINE articles are assigned 15-20 Medical Subject Headings (MeSH). 2 or 3 of those are chosen as the major points of the article, in other words, as the focus of the article.

Combine your separate sets using Boolean Logic

Use"AND" when both or all of the terms should appear
Use "OR" when either of the terms will be relevant

There are two ways in Ovid to apply evidence-based limits.

Clinical Queries
Choosing these limits applies a filter, a set of terms developed in a recent study by Haynes RB et al.

Choose the limit icon from the top menu
Scroll down to the "Clinical Queries" box.
Pick the appropriate type of search: therapy, diagnosis, etiology, or prognosis
Choose between sensitive(broad) or specific(narrow)

RCT
An alternative is to use the "Publication Type" limit, and choose "Randomized Controlled Trial" (RCT).

Often, EBM searches return only a small number of citations. It can be more time efficient to simply look at the set than to apply more limits. However, these are some quick limits you might want to consider.

Limit by date? Only the latest, or could earlier articles be important?
Limit by age group. Is your topic about a specific age group; e.g., adolescents or the elderly? (use limit icon)

Others to consider

English only? Human only

The "Search" box is located towards the top, on the left. If choosing this search option, simpler may be better. Use quotes for phrases, since the default is to "and" terms. Examples:

hypertension
"unstable angina"

If you choose to search for more than one subject, you can use either Boolean operators (AND, OR, NOT), or adjacency qualifiers (NEXT, NEAR). Example:

"antihypertensive agents" AND diabetes

Another way to conduct a simple search is to use the "Browse" feature. This allows you to look for evidence-based reviews by topic from an expandable list. Look for "BROWSE ARTICLES BY" in the main section of the web page, to the left, and click on "Topics." Pull down the menu to select a general category. An expandable list of sub-categories will appear. Follow the subject category hierarchy by clicking on the triangles to expand the categories:

Hypertension

Treatment of essential Hypertension

Pharmacological Therapies

Beta-adrenergic blocking agents

Look for the circle icon for "MeSH" at the top of the web page. (Note:This is only available on the first page; if necessary, click on The Cochrane Library 200_, Issue _ to return.)

* Type in the appropriate MeSH heading, then click on"Go To MeSH Trees." If your term is not a MeSH heading, type in one word, and click "Thesaurus" For example, "stroke" will track to several terms, including "Cerebrovascular Accident" in the Thesaurus.
*Your chosen MeSH heading will appear in the subject tree. The default mode it "Explode" which includes any more specific term indented underneath it in the subject tree.
* To select a subheading--for example, diagnosis or therapy--chose that term from the pull-down "Qualifiers" menu.
* Click on "Go"

For EBM searching,
use
"Clinical Queries"

PubMed is not Google. Break your search question into its important topics, and enter them separated by Boolean operators (and, or, not). You must use "AND" if you want all of your terms included in the articles. Use "OR" if both terms are acceptable.

As with Ovid, use subheading only if your search is broad. If you know the appropriate subheading or its abbreviation, you can enter it at the time. If not, you can use the MeSH Browser to select the relevant subheadings for your query. Some examples:

/dt drug therapy
/th therapy (includes drug therapy, surgery, prevention and control, rehabilitation...)
/di diagnosis
/tu therapeutic use (includes admin and dosage, adverse effects, contraindications...)

Limits are seldom necessary in PubMed EBM searching. Should you wish, for example, to limit by language or date, click the "Limits" link under the search box.

You can also use limits to do an evidence-based search after a general one. Do your search, click on "Limits," use the "Publication Type" limit to choose "Randomized Controlled Trial."