Question

1) Compare and contrast the 3 study approaches (Qualitative, Case-control, and Cohort) including advantages and disadvantages.

Answer 1

Epidemiological study can be classified as given above

Descriptive study is also known as the qualitative study

Qualitative study can be

Qualitative Research Designs
1.Case study
studying in-depth a single case.
The case can be an individual person, an event,
a group, or an institution

2.Ethnography
Focuses on the sociology of meaning through close field observation of
sociocultural phenomena.

3.Phenomenology
A study that attempts to understand people's perceptions, perspectives, and
understandings of a particular situatio

4.Grounded theory
Theory is developed inductively from a corpus of data acquired by a participant-
observer

5.Content Analysis
A detailed and systematic examination of the contents of a particular body of material for
the purpose of identifying patterns, themes, or biases within a material

6.Historical
Systematic collection and objective evaluation of data related to past occurrences
in order to test hypotheses concerning causes, effects, or trends of these events
that may help to explain present events and anticipate future events.

Steps in case study include

1. Defining the population to be studied
2. Defining the disease under study
3. Describing the disease by
a. time
b. place
c. person
4. Measurement of disease
5. Comparing with known indices
6. Formulation of an aetiological hypothesis

Case control study

Here the effect has already occurred and we are studying to know the exposure rate among the case and control

Steps in case control study
1. Selection of cases and controls
2. Matching
3. Measurement of exposure
4. Analysis and interpretation

CASE CONTROL
1.Proceeds from effect to cause

2.Starts with disease

3.Tests whether the suspected cause
occurs more frequently in those with
disease than those among without disease.

4.Usually the first approach for testing
the hypothesis.

5.Involves fewer no of subjects

6.Yields relatively quick results

6.Suitable for study of rare diseases

7.Generally yields only estimate of OR
Cannot yield information about diseases
other than that selected for study

8.Relatively inexpensive

9.We can calculate the odds ratio

Disadvantages of case control

1.we can't know the incidence rate

2.we can't calculate the Relative risk and attributable risk

Cohort study

Here ,we study a population and wait for incidence of a disease or cause

ELEMENTS OF A COHORT STUDY
The elements of a cohort study are :
1. Selection of study subjects
2. Obtaining data on exposure
3. Selection of comparison groups
4. Follow-up, and
5. Analysis.

In cohort study ,

1.Proceeds from cause to effect
2. Starts with healthy people
3. Tests whether disease occurs more
frequently in those exposed or in
those not exposed.
4. Reserved for testing of precisely
formulated hypothesis.
5. Involves larger no of subjects
6. Yields delayed results
7. Inappropriate for rare diseases
8. Yields Incidence, RR(Relative Risk) & AR(attributable risk)
9. Can yield information about more
than one disease.
10.expensive