LECTURE 03 2011

LECTURE 03 2011 - Outline of Randomization Lectures 1....

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Outline of Randomization Lectures 1. Background and definitions 2. Generation of schedules 3. Implementation (to ensure allocation concealment, sometimes called blinded randomization) 4. Theory behind randomization
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Readings Chapter 5 of Friedman, Furberg and DeMets Week 2 and 3 notes on the class web site Other papers are cited in the notes
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Key Points A random process should be used to generate treatment allocations or assignments Treatment allocations should be concealed until the time of randomization – “allocation concealment” is critical to prevent selection bias -- some refer to this as “blinded randomization”. (It should not be confused with blinding of treatments).
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Randomization Assignment of experimental units to treatment by a random process such that neither investigator nor patient knows the treatment to be assigned at the time the patient is registered.
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Timing of Randomized Trials 1 st patient (Chalmers) Strong degree of equipoise exists Feasibility
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Advantages of Randomization Bradford Hill : 1. Eliminates bias from treatment assignment 2. Balances known and unknown differences between groups on average 3. More credible study RA Fisher : 1. Assures validity of statistical tests
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Comparable Groups ESPRIT Study: Baseline Characteristics (N Engl J Med 2009; 361: 1548-59) IL-2 Control Total Age (median years) 40 40 40 Female (%) 19% 19% 19% Non-white race (%) 25% 24% 25% Median CD4+ cells/mm 3 (IQR) 464 450 457 (372, 584) Nadir CD4+ cells/mm 3 (IQR) 200 194 197 (91, 306) HIV-RNA < 500 copies (%) 79% 80% 80% Prior clinical AIDS (%) 25% 27% 26% Years prior ART (IQR) No. Randomized 4.1 2071 4.3 2040 4.2 (2.2, 6.4)
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Steps in Patient Registration (Randomization) 1. Patient requires treatment 2. Patient eligible for inclusion in trial 3. Clinician willing to randomize patient 4. Patient is willing to be randomized (consent is obtained) 5. Patient formally entered in trial Treatment assignment obtained from randomization list Case-report completed 6. Treatment commences
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Usual Sequence of Events in a Randomized Clinical Trial Determine eligibility + Obtain informed consent yes no randomize A B no follow-up + In many trials consent must also be obtained for screening.
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Key Elements of Informed Consent A fair explanation of the procedures to be followed, and their purposes, including identification of any procedures which are experimental A description of any participant discomforts and risks reasonably to be expected A description of any benefits to the subject or to others which may be expected A disclosure of any appropriate alternative procedures that might be advantageous for the subject
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Key Elements of Informed Consent (cont.) An offer to answer any inquiries concerning the procedures Instructions to a subject concerning the freedom to withdraw his/her consent and to discontinue participation in the project or activity at any time without prejudice or explanation Reasons study may be stopped
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LECTURE 03 2011 - Outline of Randomization Lectures 1....

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