M1: Observational Epidemiological studies Flashcards
Used to assess potential causation in exposure-outcome relationships
Observational study designs
An important subset of observational studies which (evaluate the accuracy) of (diagnostic procedures) and tests as compared to other diagnostic measures
Diagnostic study designs
3 Kinds of Diagnostic study designs
- Diagnostic accuracy
- Diagnostic cohort
- Diagnostic randomized
Group/s of individuals who are free of the outcome of
interest are classified according to levels of a suspected risk factor and (followed over a period of time) for the development of the outcome of interest
Cohort studies
5 Other terms used for cohort studies
(Pro FoIL Pan)
- Prospective
- Follow up
- Incidence
- Longitudinal
- Panel study
Advantage of Cohort studies
(Se GAME) 1. Sequencing of exposure 2. Good for rare exposure 3. Assess multiple effects of a single exposure 4. Minimized biases 5. Establish how the disease occurred \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Basically it can pinpoint the origins of a disease, especially rare ones. This can be done by sequencing as this can assess multiple effects from 1 exposure. Plus it is not biased.
5 Disadvantage of Cohort studies
(FELLL)
- Follow up bias
- Expensive
- Long follow up
- Lost follow up
- Large sample size
5 Uses of Cohort studies
- To identify risk factors for disease
- Protective factors against disease
- Prognostic factors from outcomes of disease
- To describe the natural history of disease
- To determine number of cases
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Basically to find ways to protect against disease by assessing how many people got it, how bad is it? and how the disease came to be?
Type of cohort study that (looks into the future) determination of exposure
levels (exposed vs not exposed) at baseline present and followed for occurrence of disease in the future
prospective cohort studies
Type of cohort study Going Backward. Makes use of historical data to determine exposure level
at some baseline in the past and then determine
subsequent disease status in the present
RETROSPECTIVE COHORT STUDIES
when to analyze a cohort data
when the follow-up members is complete
What to do if cohort data is is incomplete
→ No follow-up
→ Members enter into the cohort at different times
→ No longer at risk
What is used to analyze cohort data
Incidence density/rate
(Examines the relationship between a disease and other variables of interest) as they exist in a defined population at one particular point in time. Random subjects (only those who are available)
CROSS-SECTIONAL STUDIES
Method in conducting cross sectional studies
Survey or prevalence study
Use of Cross sectional studies
(HM, BED) ● Magnitude of a disease ● Hypothesis of disease etiology ● Evaluate medical care or service ● Baseline Data ● Diseases with slow onset \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Basically (I cant make a sentence so Ill enumerate in muh own words) it answers the following: 1. How wide it spread? 2. Where the hell did it come from? 3. Is our medical service good enough for it? 4. What the hell is a baseline data? 5. Is this disease slow? is it autistic?
Advantage of Cross Sectional studies
(DCEU)
● Cheap
● Easy application
● Disease rate in population and descriptive information on other characteristics
● Useful early stage detection
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Basically it is very affordable and easy to use. Helpful in early detection of a disease and providing a “Mau-ti” description of it.
Disadvantage of Cross Sectional studies
- Time
- Fluctuations
- Bias
- Cannot establish if factor is before or during the problem
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Basically it all narrows down to time, bias or uncertainty
Methods to obtain data in Cross Sectional studies
● Questionnaires ● Records ● Laboratory tests ● Physical measurements ● Special procedures
Studies the causes of disease, Chronic disease problems, Risk factors, Policy-related epidemiological research
Case control studies
Analytical style where Subjects selected on the basis of whether they do have or do not have a particular disease under study.
OBSERVATIONAL ANALYTICAL
Cases and controls are compared with respect to the proportion having a history of an exposure or
characteristics of interest
OBSERVATIONAL ANALYTICAL
Researchers assign who among the respondents are the cases and the control
OBSERVATIONAL ANALYTICAL
Advantages of Observational analytical
(FILES)
1. For diseases with long latency periods
2. Investigate rare disease
3. Less time consuming and inexpensive
4. evaluate wide range of potential etiologic exposure
5. small sample size
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Basically (I also cant summarize these so….)
1. For disease who can “nap” like Timmy
2. For disease who are like rare Pokémon
3. Very reasonable in price and practice
4. You give me: small sample size, I give you: Wide scope
Disadvantages of Observational analytical
(DIPS)
● Difficult to establish temporal relationship
● Selective survival
● Information on potential risk factors may not be available
● Present disease state of subject is likely to influence exposure factor
Case sources for observational analytical
→ Persons with the disease (hospital/facility) during a
specified period of time
→ All persons with a disease in a defined general
population at a single point in time or a given
period in time
Benefits of Hospital based control
→ Common
→ Easy
→ Less expensive
Benefits of population based control
(DAD)
→ Description of the “picture” of the disease
→ Avoidance of selection bias
→ Disease rates can be estimated
Why the need for control?
To determine if the frequency of exposure in the case group is different from that which would have been
expected
4 Issues in odds ratio
(MORSe) ● Selection bias ● Observation bias ● Recall bias ● Misclassification
is a variable that (influences both) the dependent variable and independent variable, causing a spurious association.
confounder