Clinical epidemiology investigates and controls the distribution and determinants of disease. It seeks to answer clinical questions and guide clinical decisions using evidence. Clinical epidemiology uses epidemiological methods to make predictions about individual patients by studying outcomes in similar patients groups. It aims to develop valid conclusions and avoid bias or chance influencing clinical observations and interpretations. Key elements include expressing probabilities for individual patients based on past groups, accounting for systematic errors and chance in observations, and relying on scientifically sound principles.

1. Clinical Epidemiology
Dr Vinodh Kumar O.R
Senior Scientist
Division of Epidemiology

2. Introduction
• Clinical epidemiology is a subfield of epidemiology specifically focused
on issues relevant to clinical medicine.
• The term was first introduced by John R. Paul in his presidential
address to the American Society for Clinical Investigation in 1938.
• Clinical epidemiology can be defined as the investigation and control
of the distribution and determinants of disease (Stephenson &
Babiker, 2000).
• J. M. Last - Oxymoron

3. Introduction
• The term clinical epidemiology is derived from its two parent
disciplines: clinical medicine and epidemiology.
• “Clinical“ - because it seeks to answer clinical questions and to guide
clinical decision making with the best available evidence.
• “Epidemiologic“ - because many of the methods used to answer
these questions have been developed by epidemiologists and
because the care of individual patients is seen in the context of the
larger population of which the patient is a member.

4. • It is the study of the determinants and effects of clinical decisions.
• It is the science of making predictions about individual patients by counting
clinical events in similar patients, using strong scientific methods for
studies of groups of patients to ensure that the predictions are accurate.
• Used as an aid to clinical decision making.
• Lead to valid conclusions by avoiding being misled by systematic error
(bias) and chance.

5. Purpose
• To develop and apply methods of clinical observation that will lead to
valid conclusions by avoiding being misled by systematic error and
chance.
• To foster methods of clinical observation and interpretation that lead
to valid conclusions.

6. ELEMENTS OF CLINICAL EPIDEMIOLOGY
• In most clinical situations the diagnosis, prognosis, and results of treatment
are uncertain for individual patients and, therefore', must be expressed as
probabilities.
• Probability for an individual patient is best estimated by referring to past
experience with groups of similar patients.
• Because clinical observations are made on people who are free to do as
they please and by clinicians with variable skills and biases, the observations
may be affected by systematic errors that can cause misleading conclusions.
• All observations, including clinical ones, are also influenced by the play of
chance.
• To avoid being mislead, clinicians should rely on observations that are based
on sound scientific principles, including ways to reduce bias and estimate the
role of chance.

7. Questions addressed by clinical epidemiology

8. Methods of clinical epidemiology
• Formulate question (hypothesis).
• Choose study design.
• Choose study population and sample.
• Collect and analyze data.
• Interpret results.