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ALLOCATION OF INTERVENTIONS

Learn about randomized allocation in clinical trials, including its importance, methods of generating randomized sequences, and implementation techniques. Explore the comparison of two interventions through examples.

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ALLOCATION OF INTERVENTIONS

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  1. ALLOCATION OF INTERVENTIONS • Basic workshop on randomized controlled trials • Pragmatic Randomized Controlled Trials in Health Care - Practihc

  2. OBJECTIVES Describe: • What is randomized allocation? • Why randomize? • How do you generate a sequence of randomized allocations? • How to blindly implement a sequence of randomized allocations?

  3. COMPARISON OF TWO INTERVENTIONS Example: sacarose for painfull procedures in newborns Sacarose Crying Newborns subjected to minor painfull procedures such as venous puncture or heel puncture Water Crying

  4. OBJECTIVES Describe: • What is randomized allocation • Why randomize? • How to generate a sequence of randomized allocation? • How to blindlly implement a sequence of randomized allocation?

  5. RANDOMIZED ALLOCATION • Process of allocating the intervention that trial participants will receive randomly • Each participant has a known likelihood of receiving any of the trial interventions (likelihood is usually the same) • Randomized allocation ≠ randomized sample selection

  6. COMPARISON OF TWO INTERVENTIONS Example: sacarose for painfull procedures in newborns Sacarose Cry Newborns subjected to minor painfull procedures such as venous puncture or heel puncture Water Cry

  7. OBJECTIVES Describe • What is randomized allocation • Why randomize? • How to generate a sequence of randomized allocation? • How to blindly implement a sequence of randomized allocation?

  8. REASONS TO RANDOMIZE Randomized allocation: • Controls bias during allocation creating groups with similar prognosis • Equally distributes unknown benefits and risks of interventions among participants • Establishes the base for the use of statistic methods

  9. OBJECTIVES Describe: • What is randomized allocation • Why randomize • How to generate a sequence of randomized allocation? • How to blindly implement a sequence of randomized allocation?

  10. METHODS TO RANDOMIZE 1.Fixed randomized allocation: • Simple randomization • Randomization by blocks • Stratified randomization 2. Adaptive randomizad allocation: • According to base characteristics • According to results

  11. SIMPLE RANDOMIZATION • To throw a coin or dice • To use a table of random numbers: • From a text book • Produced by a computer (i.e., Epi Info 6) • To use a program of randomized allocation

  12. RANDOM NUMBERS TABLE 229580 294531 337271 557179 019048 046523 557038 137650 242661 336328 691894 376834 941806 741721 234972 511630 907170 997146 513511 203392 321261 143797 126793 165069 081583 083023 400661 871346 538862 204934 218034 148677 634683 014067 834756 692059 672903 924007 540187 805461 209248 642823 271881 912743 793433 821197 543751 635963 548209 885131 297084 487948 819686 225092 533778 475988 383332 163481 841182 163545 940000 372299 167919 986841 886382 662876 460050 873209 594238 319556 016974 458066 682800 399191 676422 447406 018711 668340 187935 922670 ECECCC CCCECC

  13. SIMPLE RANDOMIZED ALLOCATION Advantage: • Easy to implement Disadvantage: • It could lead to unbalanced groups in terms of: • Number of subjects • Previous base characteristics of the groups

  14. IMPROPER WAYS OF SIMPLE ALLOCATION • According to the order of arrival • Deppending on the day of the week • According to the last digit of an identification number ( identity doccument, chart number,date of birth, etc.)

  15. RANDOMIZATION BY BLOCKS • Creates groups with an equal or almost equal number of individuals • Example:4 subject blocks 1. EECC 2. CCEE 3. CEEC 4. ECCE 5. ECEC 6. CECE Step 1 Step 2 10 numbers between 1 and 6 generated by Epi Info in the previous table 294531 337271

  16. RANDOMIZATION BY BLOCKS Advantages: • Balance in the number of individuals in each group • NE – NC ≤ size of the block/ 2 Disadvantages: • More complex than simple allocation • If the size of the block is known and it is not a blinded trial it is possible to predict the last allocation (EEC...C) • Data analysis is more complex

  17. STRATIFIED RANDOMIZATION • Generates groups with a guaranteed distribution of prognostic factors • Example: A trial of birth weight in pre-term newborn infants: 3 strata 1. < 1,000 g 2. 1,001 a 1,500 g 3. 1,500 a 2000 g Step 1 Step 2 Create a list of aleatorization for each stratum that can include the use of blocks

  18. STRATIFIED RANDOMIZATION Advantages: • Balance in important prognostic factors Disadvantages: • The prognostic factor should be measured in each subject before or during allocation • The total number of strata is the product of the number of subgroups for each variable • Analysis is more complex • In multicentric trials each center is a strata

  19. RANDOMIZATION SOFTWARE http://www.sghms.ac.uk/depts/phs/guide/randser.htm

  20. ADAPTIVE RANDOMIZATION 1. According to base characteristics: • The probability of allocation of an individual varies depending on the characteristics of previously asSigned subjects 2. According to the outcomes: • The probability of allocation of a subject varies depending on the results obtained form previously assigned individuals

  21. OBJETIVES Describe: • What is random allocation • Why randomize • How to generate a sequence of random allocation • How to blindly implement a sequence of random allocation

  22. BLIND RANDOMIZATION • The treatment that each subject will receive should not be known or predicted until after the subject has agreed to participate in the trial. • If the treatment can be predicted there could be bias in the allocation, especially if it is an open trial: • Subjects with certain characteristics will receive a determined allocation = no balance in the groups • It should not be confused with the blinded evaluation of the results

  23. METHODS FOR CONCEALED ALLOCATION • Opaque envelopes, sealed and numbered in sequence • Sealed packages with the medications • Randomization at the pharmacy of the institution • Centralized telephone randomization

  24. BLIND RANDOMIZATION Example1: APPIS trial - Sealed and opaque envelopes numbered in sequence

  25. BLINDED ALLOCATION Example1: APPIS trial - Sealed and opaque envelopes numbered in sequence

  26. BLIND RANDOMIZATION Example 1: Magpie trial - Boxes containing medication

  27. BLIND ALLOCATION Example 1: Magpie trial - Boxes containing medication

  28. OTHER RECOMMENDATIONS • It is desireable for someone other than the investigator to prepare the randomization • The time between the allocation of each subject and the application of the intervention should be as short as possible

  29. OBJECTIVES Describe: • What is random allocation • Why randomize • How to generate a sequence of random allocation • How to blindly implement a sequence of random allocation

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