LECTURE 11 2011

LECTURE 11 2011 - Control Groups in Clinical Trials Control...

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Control Groups in Clinical Trials
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Control Group: Definition The reference group or standard treatment against which a new treatment is compared The basis for comparison in a clinical trial Anchor for comparison Trial reports should have many phrases like “as compared to…”, “versus”, “different than”, “similar to” – all with reference to the control group.
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Types of Controls Concurrent Randomized Placebo (in lieu of treatment or on top of standard of care) No treatment Deferral of active treatment Active – Single treatment (could be a different dose of same drug) – Investigator/patient’s choice of treatment Optimized management or standard of care Dynamic treatment regime Usual care Non-Randomized Historical (e.g., patient registry) Combination of randomized and non-randomized (concurrent or historical)
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Meinert gives the following requirements for experimental and control treatments: Must be distinguishable Medically justifiable Ethically OK Both must be acceptable to patients and investigators Reasonable doubt concerning efficacy Should be reason to believe benefits outweigh risks Method of administration should be as similar as possible to real-world use Ref. Clinical Trials: Design, Conduct and Analysis
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Placebos Placebo (def.) - A medication prescribed more for the mental relief of the patient than for its actual effect on the disorder; something tending to soothe - Webster’s Dictionary A pharmacologically inactive agent to maintain blinding in a clinical trial (no specific action on the patient’s symptoms or disease)
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Angina Pectoris and the Placebo Effect (Benson, H., NEJM , 1979) Subjective improvement for five 82.4 ± 9.7% inactive treatments used prior to 1960 (13 studies, 1187 patients) Other findings : Increased exercise tolerance Reduced nitroglycerin usage Improved ECG results
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Treatment of Mild Hypertension Trial Selected self-reported side-effects (placebo versus active treatment) Weakness 18% versus 16% Headaches 34% versus 22% Muscle pain 33% versus 26%
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Example After 2nd day of treatment: Cured/ Cured Improved Antihistamine 13.4% 68.2% Effect of Antihistamine on Colds Under One Day Duration. Br Med J , 1950.
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Second Day of Treatment: Cured/ Cured Improved Antihistamine 13.4% 68.2% Placebo 13.9% 64.7%
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1) Suggestion (placebo effect) 2) Changes in course of disease Example illustrates that placebos control for: The latter, but not the former, could be controlled for with an open-label randomized study with a no-treatment control.
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Placebo Effect Subjective changes as well as objective physiological changes (beneficial and toxic) produced by placebo (not limited to psychological responses) See Beecher HK, JAMA 1955.
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Can the Placebo be the Cure? Science, April 9, 1999
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LECTURE 11 2011 - Control Groups in Clinical Trials Control...

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