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L9 - RCT Review
Review the main characteristics of RCTs
Review the…
L9 - RCT Review
- Review the main characteristics of RCTs
- Review the concepts of:
- randomization, blinding, validity
- Understand issues related to the analyses of RCTs
- Intention to treat
- Stopping rules
- To critically assess a preventive RCT
- To identify key methodological features of the study
- To identify the strengths and limitations of this study
- To summarise the key findings
- To consider the implication of the study
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General Aspects of an RCT
- Exposure/treatment determined by researcher
- Some, but not complete, control
- Intervention and Control/Comparison Group
- Random allocation of subjects to treatment or control groups
- Reduces Selection Bias and Reduces Confounders
- Blinding (Single/Double/Triple)
- Reduces Information(detection)/Performance Bias
- Eligibility Criteria
- Inclusion and Exclusion criteria for study participation are carefully developed => likely to increase internal validity, but may also reduce external validity
Can help determine the following, but only appropriate if RCT is Ethical
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Randomisation
System for assigning study subjects to treatment groups that are independent of the individual participants’ characteristics.
- Each participant should have an equal chance of being assigned to any group.
- Randomisation may either be; Simple; stratified, block (participants are grouped and randomised within groups)
Benefits of Randomisation
Groups should have a similar spread of other characteristics/confounders (sex, smoking age, weight etc.)
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Limits Influence of Confounders
As it produces comparable groups, it may eliminate known and unknown confounders
Confounders
- Associated with the exposure of interest,
- Risk factor for disease
- Can't be on the causal pathway
Blinding
May occur during;
- Randomising (Both Patients and Clinicians blind to what treatment has been administered)
- Following during the trial
- During the assessment of the outcome
- Limits Bias in reporting/measuring
- Both self report behaviours,
- Data quality cheking
- Performance Bias
Intention to Treat Analysis
- Once a patient is randomised they should be analysed in the
treatment group to which they were randomised to
- Even if they actually received the alternative treatment or do not comply with the treatment*
Example
Selection bias, consider an RCT comparing home birth vs hospital birth
If the home birth went ary and and the pregnan mother needed to be taken to hospital, and they were then included n the hospital group rather than the home group, they would skew the results of hospital births. (They might be seriously injured due to the trauma, which should be a reflection of home birthing as opposed to hospital birthing.)
If their allocation was altered then we will introduce selectio bias*
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Stopping Rules
- Developed objectively and prior to recruitment
- Beyond this, a tril may stop prematurely for several reasons;
- Success
- Poor recruitment
- Harm
- New Evidence
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Implications of this study
“Where appropriate, voluntary, safe, and affordable circumcision services should be integrated with other HIV preventive interventions and provided as expeditiously as possible.”
- Combination strategy for prevention of HIV
- Antiretroviral therapy (ART) reduces HIV transmission to uninfected partners (treatment as prevention)
- Male circumcision
- Condom use and behaviour change
- Pre-Exposure Prophylaxis
Is risk compensation an issue?
Blinding (Single, Double, Triple -Blinding)
During follow up measurements, are those involved blind to intervention
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