ORIGINAL STUDIES (primary sources) |
|
Randomized Controlled Trial |
Participants are randomly assigned to receive a given exposure (such as a new drug or therapy) and then followed to examine the effects of the exposure on outcomes. |
Cohort Study |
One or more population groups (called cohorts) are classified according to their level of exposure to a given agent/risk factor and followed over time to determine if this exposure is related to the occurrence of a disease or outcome of interest. |
Case–Control Study |
Compares individuals with a disease or outcome of interest (cases) with those who do not (controls). Researchers look retrospectively to evaluate how frequently exposure to a risk factor/agent is present in each group to identify the relationship between the risk factor and the disease or outcome of interest. |
Cross-Sectional Study |
Observes the relationship between a characteristic/risk factor (the exposure) and the prevalence of the disease or outcome of interest in a specific population at a single point in time |
Case Series |
A summary of a small group of individuals’ experience with a similar disease or outcome of interest |
Case Reports |
A summary of one individual’s experience with the disease or outcome of interest |
SECONDARY STUDIES (studies of studies) |
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Meta-analysis |
A type of systematic review in which results from available high-quality studies are statistically combined to compute a net overall effect. |
Systematic Review |
A comprehensive summary of high-quality studies examining a given topic. |
Practice Guideline (also known as Clinical Practice Guideline Evidence-Based Guideline) |
Statements that include recommendations intended to optimize patient care. Guidelines are informed by a systematic review of evidence and an assessment of the benefits and harms of alternative care options. |
Type of Question |
Ideal Type of Study |
Therapy |
Randomized Control Trial (RCT) |
Prevention |
RCT, Cohort Study, Case Control |
Diagnosis |
Prospective, blind controlled trial comparison to gold standard |
Prognosis |
Cohort Study, Case Control, Case Series/Case Report |
Etiology/Harm |
RCT, Cohort Study, Case Control |