Study design in pyramid

Question 1

order of the pyramid (7)

Answer 1

meta analysis
systematic review
practice guideline
RCT
cohort study
case control study
case reports

Question 2

case report
Definition

Answer 2

An article that describes and interprets an individual case, often written in the form of a detailed story.

Question 3

Case reports often describe:

Answer 3

Unique cases that cannot be explained by known diseases or syndromes
Cases that show an important variation of a disease or condition
Cases that show unexpected events that may yield new or useful information
Cases in which one patient has two or more unexpected diseases or disorders

Question 4

Case reports are considered the lowest level of evidence, but they are also the first line of evidence, because

Answer 4

they are where new issues and ideas emerge. This is why they form the base of our pyramid. A good case report will be clear about the importance of the observation being reported.

Question 5

If multiple case reports show something similar, the next step might be a

Answer 5

case-control study to determine if there is a relationship between the relevant variables.

Question 6

case report
Advantages
(4)

Answer 6

Can help in the identification of new trends or diseases
Can help detect new drug side effects and potential uses (adverse or beneficial)
Educational – a way of sharing lessons learned
Identifies rare manifestations of a disease

Question 7

case report
Disadvantages
(4)

Answer 7

Cases may not be generalizable
Not based on systematic studies
Causes or associations may have other explanations
Can be seen as emphasizing the bizarre or focusing on misleading elements

Question 8

case control study
Definition

Answer 8

A study that compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls), and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between the risk factor and the disease.

Question 9

Case control studies are observational because no intervention is attempted and no attempt is made to alter the course of the disease. The goal is to

Answer 9

retrospectively determine the exposure to the risk factor of interest from each of the two groups of individuals: cases and controls. These studies are designed to estimate odds.

Case control studies are also known as “retrospective studies” and “case-referent studies.”

Question 10

case control study
Advantages
(5)

Answer 10

Good for studying rare conditions or diseases
Less time needed to conduct the study because the condition or disease has already occurred
Lets you simultaneously look at multiple risk factors
Useful as initial studies to establish an association
Can answer questions that could not be answered through other study designs

Question 11

case control study
Disadvantages
(3)

Answer 11

Retrospective studies have more problems with data quality because they rely on memory and people with a condition will be more motivated to recall risk factors (also called recall bias).
Not good for evaluating diagnostic tests because it’s already clear that the cases have the condition and the controls do not
It can be difficult to find a suitable control group

Question 12

cohort study
Definition

Answer 12

A study design where one or more samples (called cohorts) are followed prospectively and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics (risk factors) are associated with it. As the study is conducted, outcome from participants in each cohort is measured and relationships with specific characteristics determined

Question 13

cohort study
Advantages
(3)

Answer 13

Subjects in cohorts can be matched, which limits the influence of confounding variables
Standardization of criteria/outcome is possible
Easier and cheaper than a randomized controlled trial (RCT)

Question 14

cohort study
Disadvantages
(4)

Answer 14

Cohorts can be difficult to identify due to confounding variables
No randomization, which means that imbalances in patient characteristics could exist
Blinding/masking is difficult
Outcome of interest could take time to occur

Question 15

RCT
Definition

Answer 15

A study design that randomly assigns participants into an experimental group or a control group. As the study is conducted, the only expected difference between the control and experimental groups in a randomized controlled trial (RCT) is the outcome variable being studied.

Question 16

RCT
Advantages
(4)

Answer 16

Good randomization will “wash out” any population bias
Easier to blind/mask than observational studies
Results can be analyzed with well known statistical tools
Populations of participating individuals are clearly identified

Question 17

RCT
Disadvantages
(3)

Answer 17

Expensive in terms of time and money
Volunteer biases: the population that participates may not be representative of the whole
Loss to follow-up attributed to treatment

Question 18

Practice Guideline
Definition

Answer 18

A statement produced by a panel of experts that outlines current best practice to inform health care professionals and patients in making clinical decisions. The statement is produced after an extensive review of the literature and is typically created by professional associations, government agencies, and/or public or private organizations.

Good guidelines clearly define the topic; appraise and summarize the best evidence regarding prevention, diagnosis, prognosis, therapy, harm, and cost-effectiveness; and identify the decision points where this information should be integrated with clinical experience and patient wishes to determine practice. Practice guidelines should be reviewed frequently and updated as necessary for continued accuracy and relevancy.

Practice guidelines are also known as “Evidence-based guidelines” and “Clinical guidelines.”

Question 19

Practice Guideline
Advantages
(4)

Answer 19

Created by panels of experts
Based on professional published literature
Practical guidance for clinicians
Considered an evidence-based resource

Question 20

Practice Guideline
Disadvantages
(4)

Answer 20

Slow to change or be updated
Not always available, especially for controversial topics
Expensive and time-consuming to produce
Recommendations might be affected by the type of organization creating the guideline

Question 21

Systematic Review
Definition

Answer 21

A document often written by a panel that provides a comprehensive review of all relevant studies on a particular clinical or health-related topic/question. The systematic review is created after reviewing and combining all the information from both published and unpublished studies (focusing on clinical trials of similar treatments) and then summarizing the findings.

Question 22

Systematic Review
Advantages
(6)

Answer 22

Exhaustive review of the current literature and other sources (unpublished studies, ongoing research)
Less costly to review prior studies than to create a new study
Less time required than conducting a new study
Results can be generalized and extrapolated into the general population more broadly than individual studies
More reliable and accurate than individual studies
Considered an evidence-based resource

Question 23

Systematic Review
Disadvantages
(2)

Answer 23

Very time-consuming
May not be easy to combine studies

Question 24

Meta-Analysis
Definition

Answer 24

A subset of systematic reviews; a method for systematically combining pertinent qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power. This conclusion is statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results.

Question 25

Meta-Analysis
Meta-analysis would be used for the following purposes:
(4)

Answer 25

To establish statistical significance with studies that have conflicting results
To develop a more correct estimate of effect magnitude
To provide a more complex analysis of harms, safety data, and benefits
To examine subgroups with individual numbers that are not statistically significant

if the individual studies utilized randomized controlled trials (RCT), combining several selected RCT results would be the highest-level of evidence on the evidence hierarchy, followed by systematic reviews, which analyze all available studies on a topic.

Question 26

Meta-Analysis
Advantages
(4)

Answer 26

Greater statistical power
Confirmatory data analysis
Greater ability to extrapolate to general population affected
Considered an evidence-based resource

Question 27

Meta-Analysis
Disadvantages
(4)

Answer 27

Difficult and time consuming to identify appropriate studies
Not all studies provide adequate data for inclusion and analysis
Requires advanced statistical techniques
Heterogeneity of study populations