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Study Methods

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Title: Study Methods Author: Sajedinejad Last modified by: sajedinejads Created Date: 6/28/2004 9:23:44 AM Document presentation format: A4 Paper (210x297 mm) – PowerPoint PPT presentation

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Title: Study Methods


1
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2
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3
  • Aim of epidemiological studies
  • To determine distribution of disease
  • (Descriptive Studies)
  • To examine determinants of a disease
  • To judge whether a given exposure causes or
    prevents disease
  • (Analytical Studies)

4
Research Methods
  • Qualitative
  • Quantitative

5
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9
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11
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12
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    ???????????? ?? ?? ???? ??? ?? ?? ?????????
    ???????.
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    ?????? ?? ??? ?????? ?? ?? ????? ???????.

13
Study Design
  • Major study designs differ based on
  • Number of observations made
  • Directionality of exposure
  • Data collection methods
  • Timing of data collection
  • Unit of observation
  • Availability of subjects

14
  • Which Design Is Best?
  • Which Design Is Best?

15
  • It depends on .
  • Regulations
  • Time urgency
  • How much is known about the association
  • Money
  • Whether the exposure is believed to be
    beneficial

16
Case Reports / Case Series
  • Case reports describe the experience of a single
    patient or group of patients with a similar DX.

17
  • Case Reports / Case Series

18
  • Case Report example
  • In 1961, a published case report of a 40
    year-old woman who developed pulmonary embolism
    after beginning use oral contraceptive

19
Important Case Reports
  • These all started with case reports - what study
    design next?
  • Lyme Disease (1975)
  • Legionellosis (1976)
  • AIDS (1981)
  • Hantavirus (1993)
  • DES exposure (1989)
  • EMS l-tryptophan (1970)
  • TSS (1980)

20
  • Case Series example
  • In Los Angeles, five young homosexuals men,
    previously healthy, were diagnosed with
    pneumocyst cariini pneumonia in a 6-month period
    (80-81)

21
  • Cross Sectional Studies

22
  • Cross Sectional Studies
  • ????? ??????
  • Yes
  • No
  • Total
  • b
  • a
  • Yes
  • ????? ??????
  • a b
  • No
  • d
  • c
  • c d
  • b d
  • a c
  • N

23
  • Cross Sectional Studies
  • ?? ?????
    ????
  • Yes
  • No
  • Total
  • 90
  • 87
  • 3
  • Yes
  • ???? ????
  • No
  • 75
  • 89
  • 14
  • 162
  • 17
  • 179

24
Prevalence Studies
  • Incident cases
  • All new cases arising in a defined population
  • Time
  • Prevalent Cases
  • Present at a point in time
  • Leave Population
  • Severe disease, Mild disease, Move
  • Early Deaths
  • Cures

25
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26
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27
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28
Case control studies
  • epidemiologists use them to study a huge variety
    of associations.
  • more frequently than other analytical studies

29
Case-control study
  • ?????? ?????? ()
  • ? --------------------------------------------
  • ?????? ?????? (-)
  • ? --------------------------------------------
  • Investigator

30
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31
Retrospective vs. prospective
  • Retrospective
  • (Case-control)
  • Disease
  • Present
  • (Cases)
  • Absent
  • (Controls)
  • Risk Factor
  • Present
  • (Exposed)
  • b
  • a
  • Prospective
  • (Cohort)
  • Absent
  • (Not Exposed)
  • d
  • c

32
  • ???? ??? ?? ????????? ??????

33
Example of an experiment
  • Population 1
  • Population 2
  • Ascorbic Acid
  • Placebo
  • Outcomes
  • Do the average number of colds differ?
  • Do their average lengths of colds differ?

34
  • TYPES OF STUDIES
  • Experimental(Interventional)
  • observational
  • Primary
  • secondary
  • (review article)
  • Narrrative
  • systematic

35
Systematic Review
  • A systematic review is an overview of primary
    studie
  • A meta-analysis is a mathematical synthesis of
    results of two or more primary studies
  • Although meta-analysis can increase the
    precision of a result, it is important to
    ensure that the methods used for the review were
    valid and reliable

36
  • The Evidence Pyramid

37
  • Intuition and Logic in Research
  • Dominant Mental Activity
  • Intuition
  • Feeling
  • Judgement
  • Experience
  • Analysis
  • Experiment
  • Clinical trials
  • Hi
  • Cohort Study
  • Case-control Study
  • Cross-sectional Study
  • Control over variance
  • Case Report
  • Case Series
  • Qualitative
  • Research
  • Lo
  • Potential for Misinterpretation
  • Lo
  • Hi

38
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39
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