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Epidemiological Study Designs

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by

Ahmed Negida

on 5 September 2015

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Transcript of Epidemiological Study Designs

Observational Studies
Observational Descriptive
Case Reports
Case Series
Observational Analytical
Cross Sectional Study
Case-Control Study
Cohort Stuay
Populations
- Target Population
- Study Population
- Accessible population
Sampling Methods
Probability VS Non-probability sampling
Phases of CTs
Randomization
Randomization as a method of experimental control has been extensively used in human clinical trials and other biological experiments. It prevents the selection bias and insures against the accidental bias. It produces the comparable groups and eliminates the source of bias in treatment assignments.
Epidemiological
Study
Designs

Interventional Studies ( Clinical Trials)
* Patients are exposed to the risk factor intentionally
* Important to test the effect of new drug/condition
* Reduce the risk to MINIMUM
* Controlled and Uncontrolled
* Phases
* Randomization (RCT - higher evidence)
* Blinding (Single/Double/Triple)
* Concealment of Allocation
* CONSORT statement (Diagram and Checklist)
* Withdrawals and ITT analysis

Case Report
* Describe new case, new event
* Important in understanding the epidemiology of
new diseases
Case Series
* Describe new case, new event
* Important in understanding the epidemiology of
new diseases
Report cases > 1
Cohort Study
Study population is classified into 2 groups
- Classification according to EXPOSURE to risk
- may start with undifferentiated sample
- PROSPECTIVE or RETROSPECTIVE
- Examples + Analysis
Cross Sectional Study
*Snap Shot in the population
*Time is not a parameter
*Used to observe associations
between group characteristics
* e.g : a cross sectional survey to measure the
prevalence of hypertension in aged persons (>65 years)
* prevalence vs incidence
* Types of population * Sampling methods !
- Examples and Analysis
1- Simple randomization
2- Clustered Sampling
3- Systematic Sampling
4- Stratified Random Sampling

5- convenience Sampling
6- Judgmental Sampling
7- Snow ball Sampling

Case Control Study
Study population is classified into 2 groups
- Classification according to OUTCOME
- Always RETROSPECTIVE
- Examples and analysis
Reviews and Other studies
* Literature Review
* Systematic Review ( Qualitative Evidence)
* Scoping Meta Review (Qualitative Evidence Mapping)
* Meta-analysis (Quantitative Evidence)
* Diagnostic test accuracy studies
* Ancillary Studies
* Secondary Data Analysis
لBlinding
Randomization as a method of experimental control has been extensively used in human clinical trials and other biological experiments. It prevents the selection bias and insures against the accidental bias. It produces the comparable groups and eliminates the source of bias in treatment assignments.
لConcealment of Allocation
It means that the person randomising the patient does not know what the next treatment allocation will be. It is important as it prevents selection bias affecting which patients are given which treatment (the bias randomization is designed to avoid).
Allocation concealment is possible with all types of trial, including unblinded trials, and is therefore universally recommended.
Blinding Levels
1- Unblinded
2- Single Blinded
3- Double Blinded
4- Double Dummy
5- Triple Blinded
CONSORT Statement
CONSORT = Consolidated Standards of Reporting Trials and encompasses various initiatives developed by the CONSORT Group to alleviate the problems arising from inadequate reporting of randomized controlled trials.
Intention to treat analysis
- started in the 1960s.
- provide unbiased comparisons among the treatment groups.
- none of the patients are excluded and the patients are analyzed according to the randomization scheme.
- provides information about the potential effects of treatment policy rather than on the potential effects of specific treatment.

Evidence Based Medicine
Judicious use of the current best evidence in making decisions about care of individual patients and improving health of the population.
Misconceptions about EBM
1- Ignores clinical Experience
2- Ignores patient values
3- Cost Cutting tool
4- Don't suit everyday practice
5- Not valuable in absence of RCTs
Full transcript