CT #1 506

All information in the file

Profile of the Framingham Heart Study

This week we are learning about the various types of studies that can be used in researching
a population for risk factors, controls versus experimental treatment, and the Framingham
heart study is introduced.
Please read the following study:
Omer, F. M., Awadalla, N. J., Alsaleem, S. A., Alsaleem, M. A., Moosa, R. A., Alqahtani, M.
A., Asiri, A. A., Alahmari, E. M., Alqahtani, A. N., & Mahfouz, A. A. (2021). Toxocara
awareness among medical practitioners in Saudi Arabia. EcoHealth, 18(1), 107–112.
Toxocara Awareness Among Medical Practitioners in Saudi Arabia | EcoHealth (springer.com)
When considering research from the perspective of ethical and legal concerns around
research in the Kingdom of Saudi Arabia.
• Describe the methods and study design used.
• Discuss the study population and participant demographics.
• Discuss the study tool and data collection plan.
• Discuss the study limitations and opportunities for future research.
Create a PowerPoint presentation of 7 content slides with discussion in the speaker notes in
addition to the title and reference slides. Speaker notes should explain your findings from
reading the study. Keep bullet points to 3–5 words.
Your well-written presentation should meet the following requirements:
•
•
•
•
The presentation shall be 9 total slides in length with 7 Content slides, however there
can be additional reference slides if needed.
Presentation notes (100-150 words) are required for each content slide. Notes must
draw from and cite relevant reference materials. Add notes to the speaker’s notes
section of the PowerPoint presentation. Submit the document in PDF format or in
speaker note view so that speaker notes can be viewed by the instructor.
Provide support for your statements with in-text citations from a minimum of four
scholarly articles in the speaker notes as well as the references slide. Two of these
sources may be from the class readings, textbook, or lectures, but two must be
external. The Saudi Digital Library is a good place to find these sources and should
be your primary resource for conducting research.
Follow APA 7th edition and Saudi Electronic University writing standards
Chapter 2
Study Designs
Learning Objectives (1 of 2)
• List and define the components of a good
study design
• Compare and contrast observational and
experimental study designs
• Summarize the advantages and
disadvantages of alternative study
designs
Learning Objectives (1 of 2)
• Describe the key features of a
randomized controlled trial
• Identify the study designs used in public
health and medical studies
Study Designs
• Observational studies
–
–
–
–
Case report/case series
Cross-sectional (prevalence) survey
Case-control study
Cohort study
• Experimental studies
– Randomized controlled (clinical) trial
Inferences
• Observational studies—inferences limited
to descriptions and associations; with
carefully designed analysis, can make
stronger inferences (statistical
adjustment)
• Experimental studies—cause and effect
In all studies—need careful definition of
disease (outcome) and exposure (risk factor)
Which Design Is Best?
• Depends on the study question
• What is current knowledge on topic?
• How common is disease (and risk
factors)?
• How long would study take; what are
costs?
• Ethical issues
Case Report/Case Series
• Observational study
• Case report—detailed report of specific
features of case
• Case series—systematic review of
common features of a small number of
cases
– Advantage: cost-efficient
– Disadvantages: no comparison group, no
specific research question
Case Series (1 of 2)
• Simplest design—description of interesting
observations in a small number of
individuals
• Usually case series do not involve control
patients (i.e., patients free of disease)
• Usually lead to generation of hypotheses
for more formal testing
• Criticisms: not planned, no research
hypotheses
Case Series (2 of 2)
• Gottleib (1981) studied five young
homosexual men with rare form of
pneumonia and other unusual infections.
• Initial report was followed by more series
(26 cases in NY and CA; “cluster” in
southern CA; 34 cases among Haitians,
etc.)
• Condition termed AIDS in 1982.
Cross-Sectional Survey (1 of 2)
• Observational study conducted at a point
in time
– Advantages: cost-efficient, easy to
implement, ethical
– Disadvantages: no temporal information,
non-response bias
Cross-Sectional Survey (2 of 2)
• Is there an association between diabetes
and cardiovascular disease (CVD)?
Patients
with
Diabetes
Patients without
Diabetes
Patients with
CVD
Prospective Cohort Study
• Observational study involving a group
(cohort) of individuals who meet inclusion
criteria followed prospectively in time for
risk factor and outcome information
– Advantages: can assess temporal
relationships
– Disadvantages: need large numbers for rare
outcomes, confounding
Cohort Study (1 of 3)
• Is there an association between hypertension and
cardiovascular disease?
CVD
Hypertension
No CVD
Cohort
CVD
No Hypertension
No CVD
Study Start
Time
Cohort Study (2 of 3)
• Identify a group of individuals that meet
inclusion criteria.
• Follow prospectively in time.
• Assess exposure.
• Evaluate outcome status.
Cohort Study (3 of 3)
• Includes persons exposed and not
exposed to risk factor at outset—usually
persons are disease free.
• Can assess temporal relationship
• Problem if disease is rare (small
numbers)
• Bias is less of an issue than in casecontrol.
• Confounding may be a problem.
The Framingham Heart Study
• 5000+ men and women enrolled in 1948
• Longitudinal cohort study
• Exams every 2 years for cardiovascular risk
factors—surveillance
• Ancillary studies—hearing, exercise, nutrition,
neurological studies
• 5000+ offspring and spouses enrolled in 1976
• Third generation enrolled in 2002
Selection of Study Sample
• Exposure group
– Common risk factors—general population
(e.g., Framingham Study)
– Rare risk factors—special exposure cohort
(e.g., soldiers exposed to agent orange)
• Comparison group
– Similar on all other factors that might affect
outcome
Case-Control Study (1 of 3)
• Observational study involving individuals
with (cases) and without (controls)
outcome of interest
– Advantages: cost and time efficient for rare
outcomes
– Disadvantages: need careful selection of
cases and controls, bias
Case-Control Study (2 of 3)
• Is there an association between sleep position
and sudden infant death syndrome (SIDS)?
Sleep prone
SIDS
Other
Sleep prone
No SIDS
Other
Study Start
Time
Case-Control Study (3 of 3)
• Select subjects on the basis of outcome.
– Cases have disease.
– Controls are free of disease.
• Compare groups with respect to proportions
with a history of exposure (possible cause).
• Investigation is retrospective in time.
Sampling
• Selection of cases
– Need explicit definition to make cases as
homogeneous as possible
– Debate over whether cases should represent all
persons with disease or specific subgroup (limit
inferences)
• Selection of controls
– Should be comparable to cases (same exclusions)
– Controls represent non-diseased persons who would
have been included as cases if they had disease.
Features
• Retrospective design
• Cost and time efficient
• Can get sufficient number of cases (useful
for rare conditions)
• Can investigate array of exposures
• Best for diseases with long latency
Issues
• Ascertainment of exposure and disease status
– Both exposure and disease have occurred—hard to
establish temporal relationship
• Bias
– Selection bias—select cases or controls and some
drop out, leaving groups not comparable
– Observation bias—knowledge of disease might
influence reporting of exposure (over-reporting
among cases)
– Recall bias—retrospective (long term)
Randomized Control Trial (1 of 2)
• Experimental study where patients are
randomized to receive one of several
comparison treatments
– Advantages: gold standard from a statistical
point of view, minimizes bias and
confounding
– Disadvantages: expensive, requires
extensive monitoring, inclusion criteria can
limit generalizability
Randomized Control Trial (2 of 2)
•
Is new drug effective in reducing hyperlipidemia (high
total serum cholesterol)?
Hyperlipidemia
Drug
No Hyperlipidemia
Sample
RANDOMIZE
Hyperlipidemia
Placebo
No Hyperlipidemia
Study Start
Time
Randomized Controlled Trial
(Clinical Trial)
• Subjects are randomized to one of two (or
more) treatments, one of which may be a
control treatment.
• In the long run, treatment groups will be
balanced in known and unknown prognostic
factors.
• Important that the treatments are concurrent—
that the active and control treatments occur in
the same period of time
• Single- versus multicenter
Features
• If possible, a study should be double blinded—
neither the investigator nor the participant are
aware of what treatment the participant is
undergoing.
• Sometimes it is impossible to blind the
participants (for example, when the treatments
being compared are medical versus surgical);
but often it is possible to ensure that the people
evaluating the outcome are unaware of the
treatment.
Phase I: Safety
• First time in humans; main objective to
assess toxicity and safety in humans—
pharmacokinetics
• Usually involves 10 to 15 patients
• Subjects are usually healthy.
• Some are placebo-controlled.
Phase II: Feasibility Study
• Focus still on safety
• Side effects and adverse events
• Efficacy is important—goal is to determine
optimal dosage.
• Involves a control group, and subjects are
randomized.
Phase III: Clinical Trial
• Focus is efficacy.
• Data are collected to monitor safety.
• Involves a control group (placebo, active
control)
• Usually involves 200 to 500 subjects
• Subjects are randomized.
• At least two centers
Phase IV: Post-Marketing
• After approval by FDA (based on efficacy
proven statistically in two or more studies,
New Drug Application (NDA) reviewed
within 1 year)
• Focus is effectiveness.
Critical Components of RCT
• Randomization
• Control group—ethical issues
• Monitoring
– Interim analysis
– Data and safety monitoring board
• Data management
• Reporting