research question and designs
TRANSCRIPT
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OVERVIEW
LN Yaddanapudi
Dept. of Anaesthesia and Intensive Care, PGIMER, Chandigarh
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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
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Developing a research question
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Research Process
Research question Background of the research Study design Study population Study variables Data Collection Quality control Statistical analysis Dissemination of data
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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
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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
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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
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Requirements Mastering the literature Being alert to new ideas and techniques
ConferencesMeet researchersSkeptical attitudeNew technologies
ImaginationObservationTeachingCreativityTenacity
Choosing a mentor
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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
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Study designs
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Descriptive studies
Case reports Case series Population studies
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Descriptive studies: Uses
Hypothesis generating
Suggesting associations
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Analytical Studies
ObservationalCross-sectionalCase-controlCohort
Experimental
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Cross-sectional studies
CharacteristicsData collected at single point of timeDescribes associationsPrevalence
StrengthsQuickCheap
WeaknessesCan’t establish cause-effect
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Case-Control Study
Start with people who have disease Match them with controls that do not Look back and assess exposures
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Case-Control Study: Strengths Good for rare outcmes Can examine many exposures Useful to generate hypotheses Fast Cheap Provides Odds Ratio
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Case-Control Study: Weaknesses
Cannot measureIncidencePrevalenceRelative Risk
Can only study one outcome High susceptibility to bias
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Cohort Study
Begin with disease-free patients
Classify patients as exposed/unexposed
Record outcomes in both groups
Compare outcomes using relative risk
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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
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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
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Clinical Trials
Randomized
Double-blind
Placebo-controlled
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Randomized Controlled Trial
Study Population
Ran
dom
izat
ion
Treatment Group
Outcome
No Outcome
Control Group
Outcome
No Outcome
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Clinical Trials
Strengths:Best measure of causal relationshipBest design for controlling biasCan measure multiple outcomes
Weaknesses:High costEthical issues may be a problemCompliance
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Clinical decisions
Evidence
Clinical Audit
Strategies to
implement guidelines
Practice guidelines
Technology assessment
Economic studies
Systematic reviews
Primary studies
Pat
ient
’s c
ircum
stan
ces
and
wis
hes