Randomized Controlled Trials
Part 1
Objectives
•
•
•
•

Identify the RCT study design
Discuss the various characteristics of RCTs
Describe measures of effecti...
Study Types

MAIN TYPES OF STUDY DESIGN
Crosssectional
Retrospective
Cohort

Observational
Longitudinal

Study Design

Pro...
Definition of RCTs
• Is a prospective study design that randomly
assigns participants into an experimental
group and a con...
Definition of RCTs
• Is a prospective study design that randomly
assigns participants into an experimental
group and a con...
Definition of RCTs
• Is a prospective study design that randomly
assigns participants into an experimental
group and a con...
RCT Study Design

Population

sample

Randomization
& Allocation
Concealment

Intervention

Disease

Placebo

NO
Disease

...
Characteristics of RCTs
www.consort-statement.org/consort-statement
Characteristics of RCTs
• Prospective:
– Allows the specific allocation and
administration of intervention to a chosen
pop...
Characteristics of RCTs
• Eligibility criteria for participants
– A comprehensive description of the eligibility
criteria ...
Characteristics of RCTs
• Settings and locations
– crucial to judge the applicability and
generalizability of a trial
Characteristics of RCTs
• Description of the interventions
– Each intervention should be thoroughly
described, including c...
Characteristics of RCTs
• Defined pre-specified outcomes
– What is the primary outcome?
– How to measure it?
– When to mea...
Characteristics of RCTs
• How sample size was determined
– The sample should be large enough to have a
high probability (p...
Characteristics of RCTs
• Randomization:
– Every participant has an equal chance of being
in either group
– Ensures that a...
Characteristics of RCTs
• Allocation Concealment.
– The treatment allocation system should thus be
set up so that the pers...
Characteristics of RCTs
• Blinding (masking)
– Withholding information about the assigned
interventions from people involv...
Characteristics of RCTs
• Statistical methods used to compare
groups
– It is essential to specify which statistical
proced...
Characteristics of RCTs
• Statistical methods used to compare
groups
– It is essential to specify which statistical
proced...
Critical Appraisal of the Evidence
It is the process of systematically
examining research to assess its validity
and relev...
Critical Appraisal of the Evidence
• What is critical appraisal?
It is the process of systematically
examining research to...
Critical Appraisal Tools
Revision 2003: information Mastery Working Group. Adapted from material developed at
McMaster University
Critically Appraise
the Evidence

Tools for Critical Appraisal

Revision 2003: information Mastery Working Group. Adapted ...
Critical Appraisal of the Evidence
• Is the study valid?

– Was the assignment of patients to treatment
randomized?
• Was ...
Critical Appraisal of the Evidence
• Is the study valid?
– Were all patients who entered the study properly
accounted for ...
Critical Appraisal of the Evidence
• Is the study valid?
– Were patients, their physicians, and study personnel
“blind” to...
Critical Appraisal of the Evidence
• Is the study valid?
– Were the groups similar at the start of the study?
• Baseline p...
Critical Appraisal of the Evidence
• Is the study valid?
– Aside from the intervention, were the groups treated
equally?
•...
Critical Appraisal of the Evidence
• Is the study valid?
– Overall, are the results of the study valid?
• Yes… No
Critical Appraisal of the Evidence
• Is the study valid?
• What are the results?
• Can I apply the results locally?
• To be continued…
randomized clinical trials I
randomized clinical trials I
randomized clinical trials I
randomized clinical trials I
randomized clinical trials I
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randomized clinical trials I

  1. 1. Randomized Controlled Trials Part 1
  2. 2. Objectives • • • • Identify the RCT study design Discuss the various characteristics of RCTs Describe measures of effectiveness in RCTs Identify tools of critical appraisal of RCTs
  3. 3. Study Types MAIN TYPES OF STUDY DESIGN Crosssectional Retrospective Cohort Observational Longitudinal Study Design Prospective Cohort Experimental Case-control
  4. 4. Definition of RCTs • Is a prospective study design that randomly assigns participants into an experimental group and a control group.
  5. 5. Definition of RCTs • Is a prospective study design that randomly assigns participants into an experimental group and a control group. • As the study is conducted, the only expected difference between the control and experimental groups is the outcome variable being studied.
  6. 6. Definition of RCTs • Is a prospective study design that randomly assigns participants into an experimental group and a control group. • As the study is conducted, the only expected difference between the control and experimental groups is the outcome variable being studied. • It is the best design to assess causality.
  7. 7. RCT Study Design Population sample Randomization & Allocation Concealment Intervention Disease Placebo NO Disease NO Disease Disease
  8. 8. Characteristics of RCTs www.consort-statement.org/consort-statement
  9. 9. Characteristics of RCTs • Prospective: – Allows the specific allocation and administration of intervention to a chosen population. – Increases the precision of the study compared to retrospective / observational data
  10. 10. Characteristics of RCTs • Eligibility criteria for participants – A comprehensive description of the eligibility criteria used to select the trial participants is needed to help readers interpret the study. – a clear understanding of these criteria is one of several elements required to judge to whom the results of a trial apply (generalizability).
  11. 11. Characteristics of RCTs • Settings and locations – crucial to judge the applicability and generalizability of a trial
  12. 12. Characteristics of RCTs • Description of the interventions – Each intervention should be thoroughly described, including control interventions. – The intensity, duration, and frequency that best balances effectiveness and safety.
  13. 13. Characteristics of RCTs • Defined pre-specified outcomes – What is the primary outcome? – How to measure it? – When to measure it? – Who will do the measurement?
  14. 14. Characteristics of RCTs • How sample size was determined – The sample should be large enough to have a high probability (power) of detecting statistically significant and/or clinically important differences – The larger the sample the better we are at measuring the effect.
  15. 15. Characteristics of RCTs • Randomization: – Every participant has an equal chance of being in either group – Ensures that all factors are equally distributed – Reduces selection and allocation biases – Eliminates the effect of confounders
  16. 16. Characteristics of RCTs • Allocation Concealment. – The treatment allocation system should thus be set up so that the person enrolling participants does not know in advance which treatment the next person will get. – Happens before the intervention starts. – Could always take place.
  17. 17. Characteristics of RCTs • Blinding (masking) – Withholding information about the assigned interventions from people involved in the trial who may potentially be influenced by this knowledge. – Participants and/or observers – Reduces observation bias. – Happens after the intervention starts. – Cannot always be implemented.
  18. 18. Characteristics of RCTs • Statistical methods used to compare groups – It is essential to specify which statistical procedure was used for each analysis, and further clarification may be necessary in the results section of the report.
  19. 19. Characteristics of RCTs • Statistical methods used to compare groups – It is essential to specify which statistical procedure was used for each analysis, and further clarification may be necessary in the results section of the report. – It is also important to describe details of the statistical analysis such as intention-to-treat analysis
  20. 20. Critical Appraisal of the Evidence It is the process of systematically examining research to assess its validity and relevance before using it to make a clinical decision.
  21. 21. Critical Appraisal of the Evidence • What is critical appraisal? It is the process of systematically examining research to assess its validity and relevance before using it to make a clinical decision. Importance to your patients (generalizability) The degree to which the results of the study are likely to be true, believable and free from bias
  22. 22. Critical Appraisal Tools
  23. 23. Revision 2003: information Mastery Working Group. Adapted from material developed at McMaster University
  24. 24. Critically Appraise the Evidence Tools for Critical Appraisal Revision 2003: information Mastery Working Group. Adapted from material developed at McMaster University
  25. 25. Critical Appraisal of the Evidence • Is the study valid? – Was the assignment of patients to treatment randomized? • Was the allocation to the different groups randomized? • How was randomization carried out? • Was it concealed?
  26. 26. Critical Appraisal of the Evidence • Is the study valid? – Were all patients who entered the study properly accounted for at its conclusion? • Less than 30% of patients did not complete the study • Duration of study sufficient • Intention to treat analysis
  27. 27. Critical Appraisal of the Evidence • Is the study valid? – Were patients, their physicians, and study personnel “blind” to treatment (masking)? • Single, double, triple blinding • How was it done? • Could there have been unblinding (unmasking)?
  28. 28. Critical Appraisal of the Evidence • Is the study valid? – Were the groups similar at the start of the study? • Baseline prognostic factors (demographics, disease severity, etc) • If different, were they adjusted for?
  29. 29. Critical Appraisal of the Evidence • Is the study valid? – Aside from the intervention, were the groups treated equally? • Co-intervention: – When participants take an intervention that has a similar effect as the intervention under study • contamination: – When participants in either of the groups receive the intervention intended for the other group • compliance
  30. 30. Critical Appraisal of the Evidence • Is the study valid? – Overall, are the results of the study valid? • Yes… No
  31. 31. Critical Appraisal of the Evidence • Is the study valid? • What are the results? • Can I apply the results locally?
  32. 32. • To be continued…

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