WEEK 1: MATCHING RESEARCH METHODS AND CLINICAL PROBLEMS Flashcards
State the 2 types of epidemiologic Study designs.
*Experimental
* Observation
State examples of experimental Study designs
- individual trial( individuals)
*Community trial ( groups)
State examples of observation study designs
- cohort studies
*Case-control study
*Cross- sectional ( prevalence) study
*Ecological study
Outline main goals of all or most designs
- to test a causal theory
*Estimate a causal parameter
*Determine relationship between exposure and outcome
E.g Exposure»>outcome
Risk factor»> disease
Independent variable»> dependant variable
What is an ideal study design like?
Observe the same study subjects under different conditions
E.g exposed and unexposed, keeping all other conditions
Describe the observational concept
Researcher does not intervene ( manipulate) only observes
Describe the observational descriptive.
*Pattern of disease occurrence (trends)
Describe by Time, Place, Person
- Planning of programs.
*Generate hypothesis test
Answer who? Where? What? How? When?
Outline reasons to carry out an observational study
- Not manipulate or randomize characteristics/ variables of interest
- Unethical to manipulate/ randomize
*Not practical to manipulate or randomize
*When it is more realistic to observe a phenomena in a more naturalistic manner
*It may be necessary to start with observation before experiment
What are descriptive prevalence studies?
Descriptive prevalence studies are observational studies that describe the patterns of disease occurrence in relation to variables such as person, place and time.
They are often the first step or initial inquiry into a new topic, event, disease or condition.
They are useful for estimating the burden of disease (e.g., prevalence or incidence) in a population.
State the characteristics of descriptive prevalence studies
*It is a snapshot of a well defined population
*It classify diseases and other variables at the same time
E.g it describes the prevalence, identify possible related factors and major impact
*are also known as cross- sectional survey or study
*Both exposure/ disease outcome are determined simultaneously
Outline the advantages of descriptive prevalence studies
*Can suggest possible risk factors of a disease
Advantages:
*They are often very easy to conduct.
*They can be conducted quickly and inexpensively.
*They can provide important information about the distribution of a disease or condition in a population.
*They can be used to generate hypotheses for further research.
State the disadvantages of descriptive prevalence studies
*uncertain temporal relationships
*Survivor effect/ health worker effect: the consistent tendency of the actively employed to have a more favorable mortality experience than the population at large
*They cannot establish causality.
*They cannot be used to determine the incidence of a disease or condition.
*They may suffer from selection bias if the sample is not representative of the population.
*They may suffer from information bias if the data is not collected accurately.
Outline the main features of a case control study
- no formal procedure of random assessments
*Subjects selected on the basis of disease status ( cases and controls)
*Past exposure is ascertained in cases and controls
State the advantages of case control studies
- sampling of cases and controls may be difficult
- Exposure may be difficult to measure retrospectively
*Prone to unique types of bias
*May have less confidence than exposure preceded disease
State the key features of a cohort study
- subjects are assigned according to exposure status
*no formal procedure of random assignment
*investigators assemble cohort on basis of exposure status - Cohort members are followed overtime to ascertain incident disease
