MEDICAL RESEARCH

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MEDICAL RESEARCH

• Dr. Harikumaran Nair.G.S
• Professor of Radiodiagnosis,
• Faculty Member CERTC,
• Medical College,
• Thiruvananthapuram

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Medical Research
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Medical Research

• A Sociologist studying villagers about their
  feelings towards immunisation,
• A Biochemist sequencing the proteins of a new
  virus.
• A statistician analysing the risk factors of a
  case control study,
• all are doing health research.

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Medical Research

• All are benefiting from the results of research
• A person who is drinking clean water from a new
  water supply tap,
• A personal taking a vitamin tablet
• Somebody jogging for cardiovascular fitness!!!!!!

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Medical Research
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Medical Research

• The strategies for
• primary health care
• child survival
• family planning
• nutrition programs
• all use the results of previous research

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Medical Research

• To have better understanding of risk factors for
  a health problem.
• For establishing the efficacy and effectiveness
  of new drugs.
• To advance basic understanding and the frontiers
  of knowledge.
• To identify and set priorities among health
  problems
• To guide and accelerate application of knowledge
  in solving health problems
• To develop new tools and fresh strategies

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Medical Research

• Locally specific research is necessary because
  intervention cannot be transferred directly from
  one location to another.
• Field studies by the Bangladesh Rural Advancement
  Committee to encourage mothers to use oral
  rehydration is a good example of locally specific
  research

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Medical Research

• Carrying out experiments/studies
• Analysing data
• Testing hypotheses
• Drawing conclusions

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Participatory vs. Top-Down Methods
Medical Research

• Both the qualitative/quantitative and
  participatory/top-down characteristics are best
  represented as continuums

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Problem based research

• Every country has its own (health) problems.
• Identification of these problems and directing
  the researchers into these areas can solve the
  (health) problems of that country satisfactorily.
  
• Better to have interdisciplinary research

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Problem based research

• Multidisciplinary research team
• Research designers
• Measurement experts
• Good evaluators
• Health economists
• Social scientists and
• Bio-statisticians etc.

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Epidemiological studies includes
Medical Research

• Research
• Programme evaluation
• Surveillance

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• Qualitative methods
• Generally do not generate specific numbers.
• They concern themselves with exploring meanings,
  processes, reasons, and explanations.
• Captured in text or diagrams, but generally not
  in numbers

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• Quantitative methods
• Statistical analysis can be done based on
  quantitative data.
• Yield summary statistics such as frequency
  distributions, means, medians, ranges and other
  measures of variation.

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• Quantitative methods
• Generate information available in the form of
  numbers, figures or numerical values
• number of people accessing government health
  centres
• number of people below or above a particular age
  group
• proportion exposed to particular risk factor .

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• Quantitative methods
• Examples of quantitative methods
• surveys.
• case control studies.
• cohort studies.

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• Research idea often props up in the mind
  during our routine .
• Refining
• Smoking ?Cancer?
• Coffee drinking ?Myocardial infarction?
• Aginamoto ?uuuuuuuu ?

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Study Design

• A study design is a method of investigation in
  medical Research for the evaluation of a health
  issue
• The investigators overall strategy for answering
  the research question.
• The choice of the design will be the first
  decision the investigator will make about how to
  proceed.

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Study Design

• various designs - different strengths and
  weakness
• some better answering some types of questions
• Feasibility and costs will also be important
  determinants of the type of design chosen.

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Case reports

• Detailed presentation of a single or a handful of
  case
• birth defects due to thalidomide
• halothane hepatitis
• new or unfamiliar diseases/rare manifestations of
  common diseases
• hypothesis generating.
• Biased reports can mislead.

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Case series

• Study of a larger groups of patients say gt10
• AIDS cases series
• No comparison

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Observational studies

• researcher gathers data by simply observing
  events.
• as they happen , without playing an active part

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Descriptive Studies

• provide important clues about possible
  determinants of a disease.

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Experimental (Intervention studies)?

• Here the researcher determines who is to be
  exposed or not .
• Of course he does not have the liberty to
  select-if randomly selected.
• He does some interventions on them
• scientifically more rigorous and strong
• feasibility less
• Sometimes can be unethical

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• Descriptive studies
• Hypothesis generating
• Analytic studies
• Hypothesis testing

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The cross-sectional study

• the most commonly used research design
• a sample is selected from a population
• information is collected from this sample at one
  point in time.

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Correlational studies

• uses data from entire populations to compare
  disease frequencies between different groups.
• refer to whole populations and not individuals
  so it is not possible to link an exposure to
  occurrence of disease in the same population .

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Cross sectional study

• one shot examinations (or surveys) of a
  population, including case and non cases.
• studied at a point or cross section in time.

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Cross sectional study
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Cross sectional study

• Defined population
• Take a Sample
• Outcome present/absent
• Astigmatism in Secondary school children
• 1000 studied , 160 had Astigmatism
• Prevalence 16

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Cross sectional study

• Only way of estimating the prevalence of
  various health problems
• Can be used to investigate likely causal
  relation ship between risk factors and a
  disease or prognostic factors and an outcome.

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Analytical studies
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COHORT Study

• Observational analytic design
• Follow up or prospective study .
• Groups are defined on the basis of presence or
  absence of exposure to a suspected risk factor of
  interest.
• Initially all will be free of disease.
• Then followed over a period of time to assess the
  development of outcome

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Exposure goup
Control group
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Cohort study design
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Cohort study design

• Prospective
• Retrospective

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Cohort study design

• INCIDENCE
• RELATIVE RISK
• The rate of an outcome(disease) in the exposed
  group is divided by the rate of that
  outcome(disease)in the unexposed.

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Incidence

• Incidence is the number of new events or cases
  of disease in a population of individuals at
  risk during a specified time interval.

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Incidence

• No of new case of a disease during a given
  period of time
• ----------------------------------------------
  --- Total population at risk

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Relative risk
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Relative risk
INCIDENCE IN EXPOSED -----------------------------
------- INCIDENCE IN UNEXPOSED A/(AB)? --------
C/(CD)?
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Case control study

• Observational analytical study where a
  hypothesis is tested comparing exposure in
  cases with exposure in controls .
• allows to get sufficient number of cases (may not
  be possible in cohort studies)

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Case control study
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Case control study
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ODDS RATIO
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ODDS RATIO
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Is 13 1 out of 3 ? or 1 out of 4 ?
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ODDS RATIO

• A/C AD
• OR ------ or -------
• B/D BC
• Multiplying diagonally across the table and then
  dividing these cross products one by the other.

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ODDS RATIO

• If frequency of exposure is higher among cases
  , the OR will be gt1 , indicating increased risk .
  
• Less than 1 shows a protective role
• The OR is approximately equal to RR when the
  incidence of that disease is very low .

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Case control study- advantages

• To study diseases with long latency periods as
  chronic diseases - Gastric Ulcer
• In rare diseases also, to study risk factors
• Can evaluate a wide range of potential
  aetiologic exposures .
• Rapid result
• Cost less than cohort studies

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Case control study- disadvantages

• Selection bias
• observation bias
• recall bias
• misclassification errors
• Temporal sequence of exposure cannot be
  established.

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Cohort Study -advantages

• correct way of establishing the risk
• correct way of establishing the incidence.
• Temporal sequence of exposure and disease can be
  established
• Rare exposures can be studied because adequate no
  of exposed and non exposed can be identified by
  the investigator.

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Cohort Study -advantages

• Multiple effects of a single exposure can be
  studied.
• More logical and direct than case control
• Selection bias less
• Good for diseases of short latency periods

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Cohort Study -disadvantages

• Expensive.
• Not useful in rare diseases.
• Bias due to loss during follow up.
• Long follow up time , so results may become
  outdated.
• Some cases unethical.

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Randomised control Study

• Most powerful study design

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Randomised control Study

• Randomisation
• Each subject has an equal chance of being in the
  intervention or control group
• Blinding
• Three levels of blinding
• Patients.
• Treatment team.
• Evaluator.

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Pyramid of research studies
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