The document discusses various study designs used in clinical research, including descriptive studies, analytical studies, randomized controlled trials, and cohort studies. It provides an overview of the characteristics, strengths, and weaknesses of different study designs. For example, it notes that case-control studies can examine many exposures but cannot measure incidence, while cohort studies provide incidence data but are time-consuming and expensive. The document emphasizes choosing an appropriate study design based on the research question.

1. LN Yaddanapudi
Dept. of Anaesthesia and Intensive Care, PGIMER,
Chandigarh

2. How to conduct a clinical
trial
 Research question
 Study designs
 CONSORT step-by-step
 Sample size and power calculations
 Randomization and blinding
 Data processing
 Simple-minded guide to hypothesis
testing

4. Research Process
 Research question
 Background of the research
 Study design
 Study population
 Study variables
 Data Collection
 Quality control
 Statistical analysis
 Dissemination of data

5. Good research depends on
 a clear question
 understanding the context of the
question
 being able to use appropriate methods
to answer the question
 knowing when to stop

6. Starting points
 Discussion with a supervisor or colleagues,
email, discussion groups, mailing lists
 Databases - Cochrane, NEXUS, Project
Impact.
 "further research needed" sections of
journal articles, papers, theses and
dissertations in the subject area of your
interest
 Topic definitions in encyclopaedias and
"state-of-the-discipline" reviews in the
journal literature

7. What are you looking for?
 topics where there is doubt and uncertainty
 disputed or contradicted statements
 topics where evidence is incomplete,
lacking, dated
 topics where evidence from a study on one
community or group could be compared
with evidence from an associated group
 topics which interest you

8. Requirements
 Mastering the literature
 Being alert to new ideas and techniques
 Conferences
 Meet researchers
 Skeptical attitude
 New technologies
 Imagination
 Observation
 Teaching
 Creativity
 Tenacity
 Choosing a mentor

9. Good research question
 Feasible
 No. of Subjects
 Technical expertise
 Affordable in time and money
 Manageable in scope
 Interesting
 Novel
 Confirms, refutes or extends previous findings
 New findings
 Ethical
 Relevant
 Scientific knowledge
 Clinical and health policy
 Future research

11. Descriptive studies
 Case reports
 Case series
 Population studies

12. Descriptive studies: Uses
 Hypothesis generating
 Suggesting associations

13. Analytical Studies
 Observational
 Cross-sectional
 Case-control
 Cohort
 Experimental

14. Cross-sectional studies
 Characteristics
 Data collected at single point of time
 Describes associations
 Prevalence
 Strengths
 Quick
 Cheap
 Weaknesses
 Can’t establish cause-effect

15. Case-Control Study
 Start with people who have disease
 Match them with controls that do not
 Look back and assess exposures

16. Case-Control Study:
Strengths
 Good for rare outcmes
 Can examine many exposures
 Useful to generate hypotheses
 Fast
 Cheap
 Provides Odds Ratio

17. Case-Control Study:
Weaknesses
 Cannot measure
 Incidence
 Prevalence
 Relative Risk
 Can only study one outcome
 High susceptibility to bias

18. Cohort Study
 Begin with disease-free patients
 Classify patients as exposed/unexposed
 Record outcomes in both groups
 Compare outcomes using relative risk

19. Cohort Study: Strengths
 Provides incidence data
 Establishes time sequence for causality
 Eliminates recall bias
 Allows for accurate measurement of exposure
variables
 Can measure multiple outcomes
 Can adjust for confounding variables
 Can calculate relative risk

20. Cohort Study: Weaknesses
 Expensive
 Time consuming
 Cannot study rare outcomes
 Confounding variables
 Exposure may change over time
 Disease may have a long pre-clinical phase
 Attrition of study population

21. Clinical Trials
 Randomized
 Double-blind
 Placebo-controlled

22. Randomized Controlled
Trial
Outcome
Treatment
Group
Randomization
No Outcome
Study
Population
Outcome
Control
Group
No Outcome

23. Clinical Trials
Strengths:
 Best measure of causal relationship
 Best design for controlling bias
 Can measure multiple outcomes
Weaknesses:
 High cost
 Ethical issues may be a problem
 Compliance

25. Clinical decisions
Patient’s circumstances
Evidence
and wishes
Clinical Audit Technology assessment
Strategies
to Practice Economic Systematic Primary
implement guidelines studies reviews studies
guidelines