The document discusses research study designs used in epidemiology, including descriptive designs like case reports and cross-sectional studies which observe characteristics at a single point in time, as well as longitudinal studies which observe the same population over multiple time periods; it also covers analytical designs like case-control and cohort studies which analyze determinants of diseases. Research design aims to objectively, precisely, reliably, and validly answer a research question by collecting and analyzing relevant data.

1. Research Study Design
Dr Qurat-Ul-Ain
Assistant Professor / HoD
Community Dentistry Department
HBS Medical & Dental College, Islamabad

2. Learning Objectives
- What is research design
- Properties of a good research design
- Classification of epidemiological studies
- Descriptive study designs
1.Case Report,
2.cross-sectional
Longitudinal studies

3. What is a Research Design?
Research is "creative and systematic work
undertaken to increase the stock of
knowledge (human health state), and use to
devise new applications.“
It involves the collection, organization, and
analysis of information (data) to increase our
understanding of a topic or issue.

4. Research has three steps:
1.Pose a question.
2.Collect data to answer the question.
3.Present an answer to the question.

5. Properties of a Good Research Design;
 Objectivity
 Precision
 Reliability
 Validity
 Generalization

6. Epidemiological Methods
Descriptive Studies
Primary focus is on describing the distribution of
disease
Analytical Studies
Primary focus is on analyzing the determinants
of disease

7. Epidemiological Study Design Strategies
• Observational vs. Experimental
• Prospective vs. Retrospective
• Cross-sectional vs. Longitudinal

8. Classification of Epidemiological Study
Design
Descriptive
(who? what? where? when?)
Observational
1. Case Reports
2. Case Series
3. Cross Sectional Studies
Analytical (why?/how?)
Observational
1. Case-control Studies
2. Cohort Studies
Experimental
3. Clinical Trials

9. Case Reports
 Case reports are considered the lowest level of evidence, but they
are also the first line of evidence, because they are where new
issues and ideas emerge.
 A good case report will be clear about the importance of the
observation being reported.
 If multiple case reports show something similar, the next step
might be a case-control study to determine if there is a
relationship between the relevant variables.

10. Case Reports
 Real-life Examples;
 This case report was published by eight physicians in New York city
who had unexpectedly seen eight male patients with Kaposiâ sarcoma
(KS). Prior to this, KS was very rare in the U.S. and occurred primarily in
the lower extremities of older patients. These cases were decades
younger, had generalized KS, and a much lower rate of survival. This
was before the discovery of HIV or the use of the term AIDS and this
case report was one of the first published items about AIDS patients.

11. Case Reports
Case reports often describe:
 Unique cases that cannot be explained by known diseases or
syndromes
 Cases that show an important variation of a disease or condition
 Cases that show unexpected events that may produce new or
useful information
 Cases in which one patient has two or more unexpected diseases or
disorders

12. Case Reports
Advantages
 Can help in the identification of new trends or diseases
 Can help detect new drug side effects and potential
uses (adverse or beneficial)
 Educational “ a way of sharing lessons learned
 Identifies rare manifestations of a disease

13. Case Reports
Disadvantages
 Cases may not be generalizable
 Not based on systematic studies
 Causes or associations may have other
explanations

14. Cross- Sectional Study
 Carried out at a single point of time or over a
short period of time
 Also called prevalence studies, as they are
normally used to estimate the prevalence of the
outcome

16. Cross sectional study
 It does not involve manipulating variables
 It allows researchers to look at numerous characteristics at
once (age, income, gender, etc.)
 It's often used to look at the usual characteristics in a given
population
 It can provide information about what is happening in a
current population

18. Cross- Sectional Studies
• Advantages:
 Inexpensive
 Take little time
 Many outcomes & risk factors maybe studies
 No loss to follow up
 Can estimate prevalence of outcome
 Useful in public health planning & evaluation, understanding disease etiology and
generation of hypothesis

19. Cross- Sectional Studies
• Disadvantages:
 ▫ Difficult to make causal inference
 ▫ Only a snapshot-may change over time
 ▫ Neyman Bias (Prevalence-incidence bias)
 ▫ Not suitable for rare conditions

20. Longitudinal Studies
 Involve repeated observations on the same
population over a period of time
 Provide information on incidence, risk factors
and natural history of disease

21. Longitudinal Studies
 Advantages:
1. Several outcomes could be studied at the same time
2. Suitable for incidence estimation
 Limitations:
1. Expensive
2. Time -consuming
3. Inefficient for rare diseases
4. May not be feasible

23. Task - 1
Cross-sectional research is;
1. a study that uses an experiment to find out why there are differences
in the study groups
2. a study that takes place at one time and examines variable in different
research groups and that variable is not manipulated by researchers.
3. a study that takes place at different times and observes changes in
one group over time

24. Task-2
 A survey conducted to evaluated caries rate in pre-school
going children and followed the same group of children till
secondary level of school to find out dietary habits and dental
caries rate. This study is;
1. Case report study
2. Cross sectional study
3. Longitudinal study
4. Analytical study