Overview of an Article:
1. Title
2. Abstract
 Overview or summary
 Highlights of results
 Statement of significance
 May be structured
3. Introduction
 State the problem
 Hypothesis or statement of purpose
4. Materials and Methods
 Study Design
 Inclusion/Exclusion criteria
 Measurement methods
 Description of techniques
 Data analysis methods
5. Results
 Findings
 Graphics/tables to summarize findings
 Statistical results
6. Discussion
 Summary of key result(s)
 Significance of the work
 Comparison with preceding publications
 Critique: limitations
7. References
 Highlight key papers in the area
 Evidence that work of others was considered
 Leads reader to additional information
Types of Articles
1. Descriptive Studies
 Purpose:
o Document experience
o Document observations
o Begin search for explanations (hypothesis generating)
 Limitations
o No explanations or causal links
o No comparisons
 Advantages
o Convenient sample
o May not require pre-planning
 Examples
o Case Report
o Clinical Series
2. Observational Studies
 Purpose
o See causes etiologies, predictors
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o Better diagnosis or outcomes
Format
o Researcher is an observing bystander
Limitations:
o Do not directly test an intervention
Advantages:
o Can limit costs
o Can validate or generate a hypothesis
Examples of observational designs:
o Case-Control - A study which selects patients who have the outcome of interest
(cases) and patients without that outcome (controls), and looks back in time to
identify characteristics that are linked to the outcome in case patients. Casecontrol studies are retrospective
o Cross-sectional -This type of study looks at a defined population at a single point
in time; it is a snapshot of what is happening at that moment in time.
Case Control
Cross Sectional
3. Experimental Studies
 Purpose:
o Evaluate efficacy of some intervention by investigator
 Format
o Researcher is intervening
o No longer a bystander
 Limitations:
o Cost
o Time
 Advantages:
o Test an intervention
 Randomized Controlled Trial (RCT) -A prospective study in which
patients are randomized into treatment or control groups. These groups
are followed up for the variables/outcomes of interest.
 Gold-standard for FDA approval
 Examples
o Clinical Trial
 Compare two antidepressant drugs
 Surgical vs. medical management of angina
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Educational Intervention
 Self instruction vs. lecture on anemia
Statistics
Three Types of Statistics:
 Descriptive Statistics
o Summarize the study data to identify important aspects of the data
 Ex. baseline demographic characteristics of study patients
 Inferential Statistics
o Test hypothesis – determine if differences between study groups are real or due to
chance
 Ex. t-test, ANOVA, Chi-square, Mann-Whitney U test
 Significance Testing
o Tests to see if something is a pattern or just chance.
o Statistical testing does not imply clinical significance
 Clinical Significance- Study results that are important enough to implement
in clinical practice. Some studies are so large that very small differences
between groups are statistically significant. But the magnitude of the benefit
may be so small that it isn’t worthwhile to adopt in clinical practice
o Lack of statistical significance does not mean lack of clinical importance
P-Value
 The level of statistical significance. A value of p<0.05 means that the probability that the
result is due to chance is less than 1 in 20.
o The smaller the p-value, the greater the statistical significance.
o The p-value does not provide any information about the size of an effect. It only
describes the strength of the result.
o P=0.045 - 4.5% probability that obs diffs occurred by chance
o Usually set at 0.05, P<0.05
 Type I Error
o concluding that two groups are different when they really are not
 Type II Error
o concluding that there was no difference between groups when in reality one existed
Validity
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The degree to which a study result is likely to be true and free of bias
Central to the critical analysis of scientific literature
Types: Internal and External
o Internal: The extent that the design and conduct of a study are likely to have
prevented bias
 More rigorously designed (better quality) trials are more likely to yield
results that are closer to the truth
 Within the confines of the study:
 Methods & analyses used bear up to scrutiny
 Results appear to be accurate
 Investigator’s interpretation appears supported
 Truth is told”
o External: The extent to which results provide a correct basis for generalizations to
other circumstances (e.g. populations or settings)
 “real-world” or typical practice
 Very important to Clinicians
 If internally valid, can the conclusions be applied to patients seen in my
practice setting?
 Good authors will help reader decide how closely study subjects mirror
patients in their practice
Bias
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A systematic error in study design that results in a distorted assessment of the
intervention’s impact on the measured outcomes
 Common types:
o Systematic differences in compared groups (Selection bias)
o Exposure to factors apart from the intervention (Performance bias)
o Participant withdrawal or exclusion (Attrition bias)
o Influence of support source (Funding bias)
 Methods to Prevent:
o Randomization
o Blinding
o Over-recruitment
 Methods to Address:
o Intention-to-treat analysis
o Disclosure
o Contributions of authors
Funding
 May include:
o Salary for investigators and/or support staff
o Cost of conducting studies
o Supply of medication & matched placebo
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Benefits & Limitations
o Benefits:
 Can be investigator-initiated research
 Often the only way to feasibly obtain medication & matched placebo
 Assistance with data management/analyses
o Limitations:
 Data control
Publication rights
Intellectual property
Not peer-reviewed
 Important in academia
 Bias results?
Endpoints and Markers
 Optimal (True) endpoints
o Longevity
o Prevention of events (reduced morbidity)
o Improvement in quality of life
 Surrogate Endpoint
o Endpoint that stands in for another endpoint
 Ex: measurement of blood pressure as a surrogate for reducing cardiovascular
events in patients with hypertension
o Validation of surrogate endpoints
 Changes in the surrogate must predict a relevant clinical outcome
AND
 Capture the effect of the intervention on the clinical outcome
 Composite Endpoint
o a combination of multiple endpoints.
o Benefit:
 Consider the goals of therapy in combination
o Limitations:
 Can be difficult to interpret
 Are all endpoints equally weighted?
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