Research Guides: Creating Searches in Medical Databases: Evauluating the Evidence

Levels of Evidence in the Primary Literature

Type of Question	Type of Study/Methodology	MEDLINE Filters
Therapy: information needed about treatments (effectiveness, cost, etc.)	Double-Blind Randomized Controlled Trial	Randomized Controlled Trial [PT] double [TW] and blind [TW]
Diagnosis: information needed about a diagnostic test (sensitivity, accuracy, etc.)	Controlled Trial	Sensitivity and Specificity [MH] Diagnosis [SH]
Prognosis: information needed about the course of the disease over time, expected complications, etc.	Cohort Studies Case Control Case Series	Cohort Studies [MH] Prognosis [MH] Survival Analysis [MH]
Etiology/Harm: information needed about causes of disease or contributing factors of disease	Cohort Studies	Cohort Studies [MH] Risk [TW]
Prevention: information needed about the prevention of disease (immunization, social factors, etc.)	Randomized Controlled Trial Cohort Studies	Randomized Controlled Trial [PT] Cohort Studies [MH] Prevention and Control [SH]
Quality Improvement: information needed about clients' and health professionals' experiences and concerns	Randomized Controlled Trial	Randomized Controlled Trial [PT] Practice Guideline [PT] Consensus Development Conference [PT]

(Abbreviations: MH=Medical Subject Heading; PT=Publication Type; SH=Subheading; TW=Text Word)

*Content Courtesy of the UIC's EBM LibGuide

Secondary Literature

Filtered or
Synthesized
Information

Description/Definition

How To Find This Type of Information

SYSTEMATIC
REVIEWS

-differ from traditional review articles in that conclusions are evidence-based rather than commentary

-start with a clearly articulated question

-use explicit, rigorous methods to identify, critically appraise, and synthesize relevant studies

-appraise relevant published and unpublished evidence before combining and analyzing data

-include description of how primary data sources are identified

-assess individual studies for validity

*Cochrane Collaboration
-Cochrane Database of Systematic Reviews
-York Database of Abstracts of
Reviews of Effectiveness
-Cochrane Controlled Trials Register
-Cochrane Review Methodology Database

*In MEDLINE:
-Review [PT] AND medline [TW]
-(Quantitative OR Systematic OR Methodologic)
AND (Review OR Overview)

*In PubMed Clinical Queries "Systematic Review" is available as a limit option.

META-ANALYSES

-specific methodologic and statistical technique for combining quantitative data

-type of systematic overview

*Cochrane Collaboration

*In MEDLINE:
-Meta-analysis [PT]
-meta-anal* [TW] OR
-metaanal* [TW]

EVIDENCE-BASED
PRACTICE
GUIDELINES

-gather, appraise, combine evidence systematically

-include statements designed to assist practitioner and patient decisions

-developed by professional groups, government agencies, local practices

-include a structured abstract: objective, option, outcomes, evidence, values, benefits/harms/costs, recommendation, validation, sponsors