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
06/15/13
1
Dr. Nisreen A. Jastaniah
Assist Prof KSAU-HS
Consultant Geriatric Medicine KAMC-J
Types Of Epidemiological StudiesTypes Of Epidemiological Studies
(Study Design)(Study Design)
Study Design
Research :
Diligent inquiry or examination in seeking facts.
Laborious or continued search after the truth.
Systematic investigation towards increasing the sum of
knowledge.
An endeavour to discover new or collect old facts by
the scientific study of a subject or by a course of
critical investigation.
Study Design
Study design:
Is the master plan specifying the methods and procedures
for collecting and analyzing the needed information.
The choice of the most appropriate design depends
largely on the objectives
Study Design
Question –Related- (P patient , I intervention ,
C comparison group , O outcome , T time )
F feasible
I interesting
N novel
E ethical
R relevant
Study design
LongitudinalDescriptive
Cross sectional
Case report
Case series
Interventional
(RCT)Observational
Case-control
Cohort
Study DesignStudy Design
Study DesignStudy Design DescriptiveDescriptive
(Cross sectional)(Cross sectional)
Qualitative study
A qualitative study explores people’s subjective
understandings of their life and experiences.
Methods used include
– Direct observation
– Interviews
– The analysis of texts or documents or recorded
speech or behavior
Study DesignStudy Design DescriptiveDescriptive
(Cross sectional)(Cross sectional)
Qualitative studies
Advantages
• Obtain views, opinions and perspectives of
individuals included in the study
• Identify themes that could may not been identified
from a quantitative study
Disadvantages
• Generalizabiltiy
Study DesignStudy Design DescriptiveDescriptive
(Cross sectional)(Cross sectional)
Study DesignStudy Design DescriptiveDescriptive
(Cross sectional)(Cross sectional)
Study DesignStudy Design DescriptiveDescriptive
CASE EPORT/SERIESCASE EPORT/SERIES
CASE REPORT/SERIES
Describe patients’ characteristics, and may generate ideas for future studies
Study DesignStudy Design DescriptiveDescriptive
CASE REPORT/SERIESCASE REPORT/SERIES
Advantages
• Useful when the disease is uncommon
• First to provide clues to identify a new disease or
adverse effect
Disadvantages
• Usually small sample size
• Only of minor relevance to public health
Study DesignStudy Design DescriptiveDescriptive
CASE REPORT/SERIESCASE REPORT/SERIES
Study DesignStudy Design Longitudinal-observationalLongitudinal-observational
Case-control studyCase-control study
Disease
No disease
(control)
Yes
No
Yes
No
Starting point
History of exposure
Compare & draw conclusions
Study DesignStudy Design Longitudinal -ObservationalLongitudinal -Observational
Case-control studyCase-control study
Advantages of
case – control studies
 Quick
 Require reasonably small numbers
 Reasonably economical
 Sensible for study of rare diseases
 No loss to follow – up
 Can test current hypotheses
Study DesignStudy Design Longitudinal - observationalLongitudinal - observational
Case-control studyCase-control study
Disadvantages of case – control studies
 Uncertain if exposure preceded disease
 Potential for recall bias (sick people may be more [or less]
likely to recall exposure)
 Selection bias (recruitment influenced by exposure)
Longitudinal - observationalLongitudinal - observational
Case-control studyCase-control study
Longitudinal – ObservationalLongitudinal – Observational
Exposed
Not exposed
(control)
Yes
No Yes
No
DiseaseFollow up
Starting point
Compare & draw conclusions
Cohort studies
Longitudinal – ObservationalLongitudinal – Observational
Cohort StudiesCohort Studies
Advantages of Cohort Study
• Can collect exposure information as exposure
happens
• Can collect multiple different exposures
• Exposure information should be relatively
reliable
• Can collect information as outcome happens
Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
Disadvantages of cohort studies
• Duration of study: may take decades to complete
• Subjects must be followed over time
• Cost: very expensive
Can you afford to wait decades for your answer?
Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
Longitudinal – ObservationalLongitudinal – Observational
Study Design & Evidence Based Clinical PracticeStudy Design & Evidence Based Clinical Practice
Different questions study design
Prevalence or frequency of factor Cross sectional
Hypotheses about possible Harm (or causes) Case-control
Harm or Causes or risk factors Cohort
Experience of illness Qualitative
Effectiveness RCT
Experimental Study Design
Study design
LongitudinalDescriptive
Cross sectional
Case report
Case series
interventionalobservational
Case-control
cohort
Experimental Study Design
A type of research that tests how well new medical
approaches work in people. These studies test new
methods of screening, prevention, diagnosis, or
treatment of a disease.
Experimental Study Design
controlled clinical trial
A clinical study that includes a comparison (control) group. The
comparison group receives a placebo, another treatment, or no
treatment at all.
Experimental Study Design
 Clinical trial
sample
intervention
control
Yes
No Yes
Noinclusion
exclusion
improved
Experimental study design
Exclusion criteria
Be parsimonious
Compelling (clinical
characteristics).
(?follow-up , compliance , high
risk).
Inclusion Criteria
Be specific
Specify populations relevant to
study question
(Demographic , Geographic ,
clinical characteristics).
Experimental Study Design
Random Assignment
Comparable groups
(Treatment & Control)
confounding variable
Is a variable in a one
group that correlate
(positively or
negatively) with the
outcome
Sample
I C
Random Allocation
Experimental Study Design
intervention group (I)
The group receiving the study agent that
is being tested in a clinical trial or
clinical study
Control group:
In a clinical trial, the group that does not
receive the new treatment being
studied.
Experimental Study Design
Blinding;
Eliminates unintentional prejudices by
those involved…
honest answers
(Single blind , double blind)
both the patients and the research staff do
not know and cannot figure out which
patients are receiving treatment and
which placebo.
Co-intervention & contamination
Blind
Co-intervention
I C
Experimental Study Design
S
I C
Drop-out
Dropout
The loss of participants during the
course of a study. (Also called loss to
follow up.)
more than 20 percent
Intention to treat
Experimental Study Design
Disadvantage
Most costly & time consuming
Randomization, blinding, placebos…
Not feasible for outcomes that are
rare or have long lag times
Sample may be very restrictive
making extrapolation difficult
Advantage
Potential for bias & confounding is
theoretically eliminated
Best design to establish cause & effect
Good Work …. Team Work
Choose mentor wisely
Get an epidemiologist / statistician
Study Design
Study design
LongitudinalDescriptive
Cross sectional
Case report
Case series
interventionalobservational
Case-control
cohort
15/06/13
38

ThankYou

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RSS study design

  • 1.  06/15/13 1 Dr. Nisreen A. Jastaniah Assist Prof KSAU-HS Consultant Geriatric Medicine KAMC-J Types Of Epidemiological StudiesTypes Of Epidemiological Studies (Study Design)(Study Design)
  • 2. Study Design Research : Diligent inquiry or examination in seeking facts. Laborious or continued search after the truth. Systematic investigation towards increasing the sum of knowledge. An endeavour to discover new or collect old facts by the scientific study of a subject or by a course of critical investigation.
  • 3. Study Design Study design: Is the master plan specifying the methods and procedures for collecting and analyzing the needed information. The choice of the most appropriate design depends largely on the objectives
  • 4. Study Design Question –Related- (P patient , I intervention , C comparison group , O outcome , T time ) F feasible I interesting N novel E ethical R relevant
  • 5. Study design LongitudinalDescriptive Cross sectional Case report Case series Interventional (RCT)Observational Case-control Cohort Study DesignStudy Design
  • 6. Study DesignStudy Design DescriptiveDescriptive (Cross sectional)(Cross sectional) Qualitative study A qualitative study explores people’s subjective understandings of their life and experiences. Methods used include – Direct observation – Interviews – The analysis of texts or documents or recorded speech or behavior
  • 7. Study DesignStudy Design DescriptiveDescriptive (Cross sectional)(Cross sectional) Qualitative studies Advantages • Obtain views, opinions and perspectives of individuals included in the study • Identify themes that could may not been identified from a quantitative study Disadvantages • Generalizabiltiy
  • 8. Study DesignStudy Design DescriptiveDescriptive (Cross sectional)(Cross sectional)
  • 9. Study DesignStudy Design DescriptiveDescriptive (Cross sectional)(Cross sectional)
  • 10. Study DesignStudy Design DescriptiveDescriptive CASE EPORT/SERIESCASE EPORT/SERIES CASE REPORT/SERIES Describe patients’ characteristics, and may generate ideas for future studies
  • 11. Study DesignStudy Design DescriptiveDescriptive CASE REPORT/SERIESCASE REPORT/SERIES Advantages • Useful when the disease is uncommon • First to provide clues to identify a new disease or adverse effect Disadvantages • Usually small sample size • Only of minor relevance to public health
  • 12. Study DesignStudy Design DescriptiveDescriptive CASE REPORT/SERIESCASE REPORT/SERIES
  • 13. Study DesignStudy Design Longitudinal-observationalLongitudinal-observational Case-control studyCase-control study Disease No disease (control) Yes No Yes No Starting point History of exposure Compare & draw conclusions
  • 14. Study DesignStudy Design Longitudinal -ObservationalLongitudinal -Observational Case-control studyCase-control study Advantages of case – control studies  Quick  Require reasonably small numbers  Reasonably economical  Sensible for study of rare diseases  No loss to follow – up  Can test current hypotheses
  • 15. Study DesignStudy Design Longitudinal - observationalLongitudinal - observational Case-control studyCase-control study Disadvantages of case – control studies  Uncertain if exposure preceded disease  Potential for recall bias (sick people may be more [or less] likely to recall exposure)  Selection bias (recruitment influenced by exposure)
  • 16. Longitudinal - observationalLongitudinal - observational Case-control studyCase-control study
  • 17. Longitudinal – ObservationalLongitudinal – Observational Exposed Not exposed (control) Yes No Yes No DiseaseFollow up Starting point Compare & draw conclusions Cohort studies
  • 18. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies Advantages of Cohort Study • Can collect exposure information as exposure happens • Can collect multiple different exposures • Exposure information should be relatively reliable • Can collect information as outcome happens
  • 19. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies Disadvantages of cohort studies • Duration of study: may take decades to complete • Subjects must be followed over time • Cost: very expensive Can you afford to wait decades for your answer?
  • 20. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
  • 21. Longitudinal – ObservationalLongitudinal – Observational Cohort StudiesCohort Studies
  • 23. Study Design & Evidence Based Clinical PracticeStudy Design & Evidence Based Clinical Practice Different questions study design Prevalence or frequency of factor Cross sectional Hypotheses about possible Harm (or causes) Case-control Harm or Causes or risk factors Cohort Experience of illness Qualitative Effectiveness RCT
  • 24.
  • 25. Experimental Study Design Study design LongitudinalDescriptive Cross sectional Case report Case series interventionalobservational Case-control cohort
  • 26. Experimental Study Design A type of research that tests how well new medical approaches work in people. These studies test new methods of screening, prevention, diagnosis, or treatment of a disease.
  • 27. Experimental Study Design controlled clinical trial A clinical study that includes a comparison (control) group. The comparison group receives a placebo, another treatment, or no treatment at all.
  • 28. Experimental Study Design  Clinical trial sample intervention control Yes No Yes Noinclusion exclusion improved
  • 29. Experimental study design Exclusion criteria Be parsimonious Compelling (clinical characteristics). (?follow-up , compliance , high risk). Inclusion Criteria Be specific Specify populations relevant to study question (Demographic , Geographic , clinical characteristics).
  • 30. Experimental Study Design Random Assignment Comparable groups (Treatment & Control) confounding variable Is a variable in a one group that correlate (positively or negatively) with the outcome Sample I C Random Allocation
  • 31. Experimental Study Design intervention group (I) The group receiving the study agent that is being tested in a clinical trial or clinical study Control group: In a clinical trial, the group that does not receive the new treatment being studied.
  • 32. Experimental Study Design Blinding; Eliminates unintentional prejudices by those involved… honest answers (Single blind , double blind) both the patients and the research staff do not know and cannot figure out which patients are receiving treatment and which placebo. Co-intervention & contamination Blind Co-intervention I C
  • 33. Experimental Study Design S I C Drop-out Dropout The loss of participants during the course of a study. (Also called loss to follow up.) more than 20 percent Intention to treat
  • 34. Experimental Study Design Disadvantage Most costly & time consuming Randomization, blinding, placebos… Not feasible for outcomes that are rare or have long lag times Sample may be very restrictive making extrapolation difficult Advantage Potential for bias & confounding is theoretically eliminated Best design to establish cause & effect
  • 35.
  • 36. Good Work …. Team Work Choose mentor wisely Get an epidemiologist / statistician
  • 37. Study Design Study design LongitudinalDescriptive Cross sectional Case report Case series interventionalobservational Case-control cohort