Observational studies observe individuals and outcomes without influencing them. There are several types including case reports, ecological studies, cross-sectional studies, case-control studies, and cohort studies. Guidelines like STROBE were created to improve reporting transparency. Upcoming developments include using clinical registries as cohort studies and propensity score matching to assemble comparable groups. Observational studies provide important descriptive data and can study long-term outcomes unlike clinical trials.

1. Observational Studies and their
Reporting Guidelines
Dr. Kopal Sharma
Senior Demonstator
SMS Medical College, Jaipur

2. Outline of presentation
• Definition
• Study designs
• Types of observational studies
• Guidelines for reporting of observational
studies
• New types of observational studies
• Conclusion

3. Definition
• A type of study in which individuals are observed or
certain outcomes are measured. No attempt is made to
affect the outcome.
• The intent of observational studies is to investigate:
- the ‘natural’ state of risk factors,
- diseases or outcomes.

6. Types of Observational Studies
- Case reports and case series
- Ecological studies
- Cross-sectional studies
- Case-control studies
- Cohort studies

7. Case Report or Case Series
• Serve a useful role in describing new or notable events in
detail. These events often warrant further formal
investigation.
• Examples :
- Reports of unexpected benefits or adverse events, such as
a case report describing the use of high-dose quetiapine in
treatment resistant schizophrenia after intolerance to
clozapine.
- A case report of a medication error involving lookalike
packaging.

8. Ecological Studies
• Ecological studies are based on analysis of
aggregated data at group levels (for example
populations), and do not involve data on individuals.
• Typical examples include studies that examine
patterns of drug use over time. Comparison of the use
of non-steroidal anti-inflammatory drugs and COX-2
inhibitors in Australia and Canada.

9. • They describe associations between drugs and
outcomes, such as changes in the rates of upper
gastrointestinal haemorrhage after the introduction of
COX-2 inhibitors.
Demerit : Individual-level data are not presented.

10. Cross – Sectional Studies
• Cross-sectional studies collect data at a single point in
time for each single individual, but the actual data
collection may take place over a period of time or on
more than one occasion.
• There is no longitudinal follow-up of individuals.
• Provide a profile of a population of interest, which may
be broad. Eg. the Australian Health Survey undertaken
intermittently by the Australian Bureau of Statistics.

11. Case-Control Studies
• Case-control studies focus on determining :
- Risk factors for an outcome of interest (such as a
disease or a drug’s adverse effect) that has already
occurred.

12. Steps in Case-Control Studies
First
- Two groups of participants are assembled:
a) those who already have the outcome (cases)
b) those who do not have the outcome (controls), who
are often matched to the cases to make them similar
and reduce bias

13. Second
• Data on previous exposure to selected risk factors are
collected.
• And compared to see if these risk factors are more (or
less) common among cases versus controls.

14. Case – Control Studies
• Multiple risk factors can be studied, but each case-
control study can involve only one outcome.
• Example: case-control study explored the risk factors
for the development of flucloxacillin-associated
jaundice (outcome).

16. Cohort Study
• In a cohort study, an outcome or disease-free study
population is first identified by the exposure or event of
interest.
• And followed in time until the disease or outcome of
interest occurs.
• Exposure is identified before the outcome, cohort studies
have a temporal framework to assess causality and
potential to provide the strongest scientific evidence.

19. Advantages of Observational Studies
• Relatively quick
• Inexpensive
• Easy to undertake.
• Can be much larger than randomized controlled trials
so they can explore a rare outcome.
• Undertaken when a randomized controlled trial would
be unethical.

20. STROBE Statement
• 2004- the first meeting of the Strengthening the
Reporting of Observational Studies in
Epidemiology (STROBE) group took place in
Bristol, UK.
• Aim :
- To establish guidelines on reporting observational
research to improve the transparency of the methods,
thereby facilitating the critical appraisal of a study's
findings.

21. • A well-designed but poorly reported study is
disadvantaged in contributing to the literature because the
results and generalizability of the findings may be
difficult to assess.
• Thus a 22-item checklist was generated to enhance the
reporting of observational studies across disciplines.
• This checklist is also located at the following
website: www.strobe-statement.org.

26. Upcoming Developments
• Clinical registries are essentially cohort studies, and
are gaining importance as a method to monitor and
improve the quality of care.
• Allows for the identification of variations in clinical
practice and benchmarking across practitioners or
institutions.
• These data can then be used to develop initiatives to
improve evidence-based care and patient outcomes

27. Propensity Score Matching
• Propensity score matching is a way to assemble two
or more groups for comparison so that they appear
like they had been randomized to an intervention or a
comparator.
• The method involves logistic regression analyses.

28. Conclusion
• While clinical trials remain the best source of
evidence regarding the efficacy of drugs,
observational studies provide critical descriptive data.
• Observational studies can also provide information on
long-term efficacy and safety that is usually lacking
in clinical trials.