Using PubMed to Search for Evidence: Clinical Queries

Clinical Queries offers a user-friendly approach to evidence-based searching on the Medline database. Designed for busy practitioners, this specialized interface provides fast access to reliable clinical studies. Clinical Queries is divided into three sections:

Clinical Studies, uses pre-set research methodology filters, developed by RB Haynes, Ann McKibbon, and others at McMaster University, enable the searcher to quickly locate the relevant literature on etiology, prognosis, diagnosis and therapy of diseases and diagnostics. These filters were revised in 2005. Also included in the Clinical Queries interface are utilities for finding Systematic Reviews and articles concerning Medical Genetics. While this fact-sheet is intended to guide you through the Clinical Studies section of Clinical Queries, the same information can be used when searching either the Systematic Reviews or Medical Genetics sections.

The utilities in Clinical Queries are not intended to supply a comprehensive literature search. They are designed to provide information on those few "good" articles which will help the clinician make informed health-related decisions. The following search tips are intended as a guide to performing a basic search using the Clinical Studies utility.

Selecting the Filters: Categories 

Clinical Studies offers five clinical study categories to choose from:

• Therapy: The therapy filter will retrieve clinical studies that discuss the treatment of diseases. You will notice that therapy is the search default.
• Diagnosis: Click on diagnosis to find clinical studies addressing disease diagnosis.
• Etiology: Click on etiology to find clinical studies addressing causation/harm in disease and diagnostics.
• Prognosis: Click on prognosis to find clinical studies addressing disease prognosis.
• Clinical Prediction Guides: Click on clinical prediction guides to find clinical studies which discuss methods for predicting the likelihood of disease presence or absence.

Selecting the Filters: Emphasis 

Clinical Studies offers two emphasis categories to choose from:  

• Broad, sensitive search: Click on the sensitivity filter to find mostly relevant articles. Less relevant articles will also be included in this emphasis. Choose this filter to find a greater total number of articles for your query when you want to browse the literature.
• Narrow, specific search: You will notice that specificity is automatically selected. This option will retrieve the articles most relevant to your query, and therefore will limit the total number of articles found. Some less relevant articles may also be retrieved. Choose this option to refine your search results to the articles most relevant to your query.

Inputting the Search 

Now you are ready to type in the subject. It is best to use specific subject terms. For example, if you want clinical studies on the treatment of atrial fibrillation, type in atrial fibrillation. Do not enter "heart disease". Using the most specific term will help you retrieve the articles that best match your need. Some useful tips to remember are:

• Grammar does not count. Syntax does not count. You do not need to capitalize your terms. Think of your terms as nouns. For example, type in the name of the disease or diagnostic test you want information on:
  • Psoriatic arthritis
  • Positron emission tomography
  • Gastroenteritis
• Do not enter abbreviations for diseases. Type in coronary artery disease, not CAD.
• If you want to search for synonymous terms, such as trigeminal neuralgia or tic doloreaux, capitalize the OR connector and type your terms this way:
  • Trigeminal neuralgia OR tic doloreaux
• If you want to combine two discrete concepts capitalize the AND connector:
  • Myocardial infarction AND Adrenergic beta-Antagonists

Limiting the Search

Clinical Studies will not automatically limit your search to the most recent publications or to English language publications. Unless you limit your search, all dates back to 1950 and all publication languages will be searched.

Limiting the Search: Limit by Year

Limit by one year: To limit to a specific year is simple. After running your search, click on the "limits" tab directly above your search results. Locate the box "Dates". From the Drop Down Box "Published in the last", select "1 Year".

Limit by range of years: Let's say you'd like information on AVM's from 2002 through 2006. To do so, select the box "Dates" under the "Limits" tab. From the Drop Down Box "Published in the last", select "Specify Date Range". This will expand the "Dates" box. The Publication date box will permit you to limit to a particular month, day and year, should you so desire!

Limiting the Search: Limit by Language

To indicate that you'd like to limit your search to a specific publication language, use the "Limits" tab and scroll down to "Languages" box. Then, select those languages from the long list provided. You may limit to as many languages as you desire. The more commonly requested languages (English, French, German, Italian, Japanese, Russian, Spanish) are listed first, with the other choices listed below them.

Limiting the Search: Other Limits

You may use the "Limit" tab to set several other limits, including age of the patients in the studies, sex of the patients, limitation to human or animal subjects. Once activated, the limits that you have selected will apply to all searches within your session. Be sure to "turn off" the limits by unclicking the limits tag, should you want to eliminate these choices for your next search.

A Word of Caution

Once you see your article set, there is an option " related articles". By selecting that option, you eliminate the filters of the Clinical Study search (and any limitations that you’ve selected, such as language or year(s)). So, use "related articles" with caution; remember, your search is no longer evidence-based.

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