experimental studies. types of experimental studies multiple experimental groups blinds single,...
TRANSCRIPT
![Page 1: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/1.jpg)
Experimental Studies
![Page 2: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/2.jpg)
Types of Experimental Studies
• Multiple experimental groups
• Blinds single, double, triple
![Page 3: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/3.jpg)
Public Health & Clinical Objectives
• Modify natural history of disease and express disease prognosis Prevent or delay death or disabilityImprove health of patient or population
• Need to use best preventive or therapeutic measuresRandomized trials are ideal design to
evaluate effectiveness and side effects of new forms of intervention
![Page 4: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/4.jpg)
Historical Perspectives
• Sir Francis Galton (1883) - ruminated over the influence of prayer
• Joyce and Welldon (1965) found no benefit of prayer
• R. C. Byrd (1988) - suggested positive benefits
• Washington Post Parade article (2003) - also suggested positive benefits
![Page 5: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/5.jpg)
![Page 6: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/6.jpg)
Recent Perspectives
• Effect of: coffee on CHDcarotene on cancershormonal therapy on breast cancerdrug-lowering cholesterol on CHD
![Page 7: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/7.jpg)
Randomized Trials
• Historically, were done accidentally, in other words, “unplanned trials”Ambroise Pare (1510 - 1590) discovered
new treatment for war wounds when original therapy was unavailable
James Lind (1747) studying scurvy
• Subjects assigned to groups using a non-biased procedure
![Page 8: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/8.jpg)
Design of a Randomized Clinical Trial
![Page 9: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/9.jpg)
Selection of Subjects
• Well-designed
• Eliminate subjectivity
• Promote reliabilityReplicable, as with laboratory
experimentsAccurate
![Page 10: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/10.jpg)
Selection of Subjects: Studies without Comparison
• Question: If we administer a drug and the patient improves, can we attribute the improvement to the administration of that drug?
• Answer: Results can always be improved by omitting controls.
- Prof. Hugo Muensch Harvard University
![Page 11: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/11.jpg)
Selection of Subjects: Studies with Comparison
• Historical controls (comparison group from past)Data must be abstracted from records not
kept for research purposesDifferences may be due to quality of the dataMay not be able to substantiate differencesCan be useful for drugs developed against
fatal diseases
![Page 12: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/12.jpg)
• Simultaneous Non-Randomized Controls May introduce biasExample - BCG vaccination study in NYC in
1975 • Investigators introduced selection bias in the
experimental group and controls• A change in the study design that eliminated
selection bias, although still not randomized, also eliminated differences observed in final results
Selection of Subjects: Studies with Comparison (cont.)
![Page 13: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/13.jpg)
![Page 14: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/14.jpg)
![Page 15: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/15.jpg)
• Best approach
• Uses tables of random numbers
• Must still eliminate physician bias
• Can achieve non-predictability
Selection of Subjects (cont.):
Randomization
![Page 16: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/16.jpg)
![Page 17: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/17.jpg)
Effect of Comparability
Not Randomized Randomized
![Page 18: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/18.jpg)
Selection of Subjects (cont.):
Stratified Randomization• Useful when concerned that certain
variables may affect the outcomeFor example, when the prognosis may be
much worse for older patients • Want two treatment groups to be
comparable in terms of the variables of concern
• Initially stratify (layer) the study population according to each variable of concern and then randomize participants to treatment groups within each stratum
![Page 19: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/19.jpg)
Selection of Subjects (cont.):
Stratified Randomization
![Page 20: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/20.jpg)
Data Collection on Subjects:Potential Variables
• Treatment: that was assigned that was received
• OutcomeExplicit criteria requiredComparable measurements required
• Prognostic Profile at Entry If risk factors for a bad outcome are known,
assure that treatment groups are reasonably similar for these factors
Data for prognostic factors obtained upon enrollment in study
• Masking (Blinding)
![Page 21: Experimental Studies. Types of Experimental Studies Multiple experimental groups Blinds single, double, triple](https://reader035.vdocuments.net/reader035/viewer/2022062511/551c491e550346b1458b4922/html5/thumbnails/21.jpg)
Data Collection on Subjects (cont.):
Masking (Blinding)
• Attempt to eliminate biases & preconceptions• Single-blind
Subject masking Use of placebo
• Double-blindSubject masking and researcher masking
• Data collectors and data analysts
• Triple-blindSubject masking, researcher masking and study
sponsor masking