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INTERVENTIONS

INTERVENTIONS. Basic workshop on randomized controlled trials Pragmatic Randomized Controlled Trials in Health Care - Practihc. OBJECTIVES. Describing: What a study variable is The role of variables in a randomized trial (interventions, outcomes, confouders)

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INTERVENTIONS

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

  2. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

  3. CONTROLLED TRIALS Selection Follow up Assignment Measurements and comparison Intervention Eligible subjects, who have not presented the outcome of interest Exp Outcome frequency Outcome frequency Control

  4. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

  5. VARIABLE “Any atribute, phenomenon or event that may have different values. Any ammount that varies.” Last JM. A Dictionary of Epidemiology, Oxford University Press, 1983

  6. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

  7. RANDOMIZED TRIAL VARIABLES • Interventions (independent) • Outcome(s) (dependent(s)) • Confounders • Others (i.e., population characteristics)

  8. RANDOMIZED TRIAL VARIABLES Example: Magpie trial • Interventions (independent): • Magnesium sulphate or placebo • Outcomes(s) (dependent(s)): • Main: frequency of convulsiones (eclampsia) • Secondary: death rates in women and newbors, adverse events adversos, hospitalization rates • Confounders: • Gestational age, women´s age, multiple pregnancy, socio-economical background, etc. • Others (population characteristics): • Parity, nutritional status, etc.

  9. ELEMENTS OF A WELL-RAISED QUESTION (PICOT) 1. P: population or characteristics of the implicated subjects 2. I: intervention or exposure that the person or the population experiments (preventive or curative intervention) 3. C: control to which the exposure is compared 4. O: outcome measures of interest 5. T:the target of the trial; is the intervention better? is the intervention as good (“non-inferior”)?

  10. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

  11. TYPE OF INTERVENTIONS • Many types: • Vaccines • Medicines • Surgical procedures • Educational programs • Physical therapy and rehabilitation • Undergoing a diagnostic test • It is important to describe the interventions as completly as possible (to allow reproducing them)

  12. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

  13. TRIAL INTERVENTIONS • Experimental: • The new intervention • The “new” indication / dose / administration form of an “old” intervention • Control: best available treatment for the condition: • Other medical or surgical treatment • Usual treatment plus placebo • Only placebo • Nothing

  14. TRIAL INTERVENTIONS Purely explanatory trial: • Does the intervention work under ideal conditions? • It may require a “control” without treatment (if feasible ethically) Purely pragmatic trial: • Does the intervention work under usual conditions? • The contrl groups receives tha best available treatment

  15. REQUEREMENTS FOR EXPERIMENTAL AND CONTROL INTERVENTIONS • They must be different from each other • They must be medically justified • Ethical basis for using them • Medically required • Acceptable for both subjects and researchers • Real uncertainty about the experimental intervention value • Potential benefits are perceived as larger than potential risks • Delivery similar to real world

  16. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

  17. PLACEBO EFFECT • Effect (usually, but not always, positive) attributed to the expectation that a therapy will have an effect. • The effect is due to the power of suggestion • Placebo: a inert medication or procedure Last JM. A Dictionary of Epidemiology. 1983. New York, Oxford University Press

  18. SUMATRIPTAN Nasal MANEJOAGUDO MIGRAÑA % Alivio de dolor a las 2 horas 70 64 63 62 60 55 60 50 35 40 32 29 25 25 30 20 10 0 Study 1 Study 2 Study 3 Study 4 Study 5 Sumatriptan Placebo

  19. TRIAL INTERVENTIONS • If there is an effective standard intervention: • Subjects in control group should not receive only placebo • It must be given to subjects in the control group; if needed, they can also receive a placebo • Participants must understand that they could be receiving a placebo, and the chances of receiving it

  20. OPEN AND BLIND (MASKED) TRIALS • Blind, masked: someone (participants, clinicians, researchers) ignores the intervention that each subject is receiving: • Single-blind: some of them do not know • Double-blind: none of them know • Open: participants, clinicians and researchers know the intervention that each subject is receiving

  21. OBJECTIVES Describing: • What a study variable is • The role of variables in a randomized trial (interventions, outcomes, confouders) • The principles for defining the experimental intervention in a trial • The principles for defining the control intervencion in a trial (active intervention, placebo, nothing) • Defining placebo effect and placebo

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