Evidence-Based Medicine 1
Knowledge and Skills for Critical
Reading
Karen Schetzina, MD, MPH
Overall Objective
Become familiar with research methods
and explore issues that may lead to future
research interests, community service
activities, advocacy projects, or focuses of
study in your career.
Epidemiology
The study of the distribution and
determinants of health-related
states or events in specified
populations, and the application
of this study to the control of
health problems
Assumptions
Disease does not occur at random but is
related to environmental and /or personal
characteristics
Causal and preventive factors for disease
can be identified; knowledge of these
factors can then be used to improve
health of populations
Purposes of Epidemiologic
Studies
Identify new diseases
Identify populations at risk for a disease
Identify possible causative agents of a
disease
Identify factors or behaviors that increase
risk of disease and their relative
importance
Purposes of Epidemiologic
Studies (continued)
Rule out factors or behaviors as
contributing to a disease
Evaluate therapies for a disease
Guide in the development of effective
public health measures and preventive
strategies
Reading Epidemiologic Studies
Become familiar with medical terminology
(but you don’t need to know every word)
Have some prior knowledge of the
pathophysiology of the disease of interest
Understand principles of study design,
analysis, and interpretation
Pneumocystis Pneumonia
--- Los Angeles
Background Info/Definition of Terms
Opportunistic infections – occur only in persons with
abnormal immune systems
Pneumocystis carinii pneumonia
Cytomegalovirus (CMV) infection
Candidiasis/candida mucosal infection – yeast infection
Leukopenia / neutropenia – low white blood cell count
Viruria – virus detected in urine
Titre – antibody count
Neoplasia - cancer
Hodgkins Disease – a type of lymphoma (cancer)

Clinical Correlations
“Pneumocystis Pneumonia– Los
Angeles”
“First Report of AIDS”
Pneumocystis carinii pneumonia
(PCP)
• Caused by a microorganism
• Frequently seen in persons with
compromised immune systems:
AIDS patients
Elderly
Premature babies
• Presentation
Fever
Shortness of breath
Nonproductive cough
(Bilateral infiltrates- chest x-ray)
Cytomegalovirus (CMV)
Group of herpesviruses
Often infections are asymptomatic
If symptoms present:
Mononucleosis-like illness
Candidiasis (thrush)
Pneumocystis Pneumonia
--- Los Angeles
 What type of article is this?
 What do you think is/are the purpose(s) of the article?
 From what population are the subjects of this report
derived?
 What similarities between the cases were mentioned in
the article?
 What conclusions did the editor reach?
 What are the limitations of this type of report in terms of
the information it provides?
 What are the public health implications of this report?
 What questions arise after reading this report? What
future research is needed?
Anatomy of a Journal Article
Abstract
Introduction / statement of the problem
Methods
Results
Discussion
References
Definitions
Hypothesis or research question
Population – Collection of units from which a
sample may be drawn
Sample – A selected subset of a population
Variable - “Any quantity that varies. Any
attribute, phenomenon, or event that can have
different values.”
Predictor Variable – Risk factor
Outcome Variable – Disease or condition of
interest
Association or Correlation – Degree to which
variables change together
Definitions
Estimate – Incorporates some degree of error
Prevalence - “The number of events in a given
population at a designated time”
Incidence – “The number of new events in a
defined population within a specified period of
time”
Mean – average
Variance – A measure of dispersion or variation
Standard Deviation/Error – Square root of the
variance
Study Designs
Observational, Descriptive
Observational, Analytic
Experimental
Study Designs
Observational, Descriptive
Describe the amount and distribution of
disease
Useful for generating hypotheses
Observational, Analytic
Designed to test one or more specific
hypotheses
Experimental
The exposure and the persons to be exposed
are determined by the investigator
Study Designs
Observational, descriptive
Case reports, case series
Ecological
Cross-sectional
Observational, analytical
Case control
Cohort
Experimental
Randomized clinical trial
Community Intervention Trial