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Factors determining study design
- ability to answer primary research question
- potential new treatment
- probability of risk to participants
- probability of participants likely to benefit
- size & accessibility of studied population
- how data is used
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investigators will take the primary research question and develop
- a hypothesis to test
- very important when trying to evaluate the study
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observational studies are good for
discovering things that need to be investigated further
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interventional studies are good for
investigating the effect of a particular change
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Prospective study characteristics
- forward in time
- gather data on events as they happen
- creating chart
- interventional trials
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retrospective trial characteristics
- backward in time
- gather data from historical documentation
- looking at chart
- subject to recall bias
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observational trials may be
pro or retrospective
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uncontrolled trial characteristics
- results of one group's experince
- can't determine cause and effect
- interventional or observational
- no "control group"
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Controlled trial characteristics
- One group's results compared to results of group not experiencing event
- two or more groups
- interventional or observational
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when determining efficacy, the control is
placebo
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when determining efectiveness/efficaciousness the control is
active
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Dose comparison trial controls are
two different doses along with placebo group
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Randomized trial characteristics
- must have 2 or more groups
- individuals randomly assigned
- may be possible in retrospective studies
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Non-randomized trial characterizations
- may be 1 or more groups
- individuals assigned to group based on certain traits or by choice of investigator
- groups may not be similar
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when factors are known that are highly likely to affect the results or be predictive of disease progression
- stratification
- ie: try to put the same number of smokers in each group
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Parallel trial characteristics
- two or more groups have different experiences at the same time
- most common
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cross-over trial characteristics
- one group having two or more experiences at different times
- each individual serves as his own control
- "paired data"
- smaller groups required
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advantages of Study diagrams
- visual aid
- understand complex study designs
- identify potential problems
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Single Blinded trial characteristics
either pt or investigator knows assignment
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double blinded trial characteristics
- neither patient nor investigator knows assignments
- more objective observation of results
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Un-Blinded trial characteristics
- investigator and pt know what group pt is in
- outcomes may be reported differently
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Inclusion criteria
- "to be in the study, pt must..."
- aids in addressing hypothesis
- "fine-tune" a diagnosis
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Exclusion criteria
- "to be in the study, a pt must not..."
- reduces risk and complications for pt
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single study site
- smaller numbers of pt
- easy communication
- easy data collection
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multiple study sites
- large number of pt
- challenging to coordinate research efforts
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Type I clinical study
- prospective
- interventional
- controlled
- statistical power
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Type II clinical study
- prospective
- interventional
- controlled
- no power
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Type III clinical study
- prospective
- observational
- comparison groups
- cohort studies
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Type IV clinical study
- retrospective
- observational
- comparison groups
- case control study
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Type V clinical studies
- prospective
- interventional or observational
- uncontrolled
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Descriptive study designs
- document and communicate experience
- share observations & unusual events
- case report or series
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Explanatory study design
- examin cause
- efficacy/etiology using method of comparisons
- clinical trials, case controls, cohorts, cross-sectional
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Examples of interventional/experimental studies (clinical trials)
- superiority
- non-inferiority
- equivalency
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Observational studies seek
- causes
- etiologies
- predictors
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examples of observational studies
- cohort
- case control
- cross-sectional
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Cohort study
- prospective or retrospective
- observational
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Case Control Study
- retrospective
- observational
- match a person with an outcome of interest to a similar person without and look for differences in variables
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cross sectional study
- slice in time
- observational
- blend of cohort and case study
- prevalence study
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