randomized clinical trials II
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The document discusses key aspects of randomized controlled trials (RCTs) including study designs, characteristics, and methods for critical appraisal. RCTs are considered the gold standard for evaluating interventions as randomization reduces bias. Key characteristics discussed include eligibility criteria, interventions, outcomes, sample size calculation, allocation concealment, blinding, and intention-to-treat analysis. Statistical methods to analyze RCT data and compare groups are also presented, such as relative risk, odds ratios, and number needed to treat. Tools for critical appraisal include considering the precision of treatment effect sizes, applicability of results, and weighing benefits versus harms.
randomized clinical trials II
- 2. Outcomes • • • • 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. Study Types MAIN TYPES OF STUDY DESIGN Crosssectional Retrospective Cohort Observational Longitudinal Study Design Prospective Cohort Experimental Case-control
- 4. RCT Study Design Population sample Randomization & Allocation Concealment Intervention Disease Placebo NO Disease NO Disease Disease
- 5. Characteristics of RCTs • • • • • • • • • Prospective: Eligibility criteria for participants Settings and locations Description of the interventions Defined pre-specified outcomes How sample size was determined Allocation Concealment Blinding Statistical methods
- 6. Characteristics of RCTs Statistical methods used to compare groups • Intention-to-treat analysis Experimental (composite) Control (Amalgam) 100 100 20 ?? 80 8F 12 8/80 = 10% 100 72 S 8 20/100= 20% 20 F 80 S 20/100= 20%
- 7. Characteristics of RCTs Statistical methods used to compare groups • Intention-to-treat analysis Experimental (composite) Control (Amalgam) 100 100 20 ?? 80 8F 20 28/100= 28% 100 72 S 20 F 80 S 20/100= 20%
- 8. Characteristics of RCTs Statistical methods used to compare groups • Intention-to-treat analysis • Analysis by which all participants are included in the arm to which they were allocated, whether or not they received (or completed) the intervention given to that arm. • Intention-to-treat analysis prevents bias caused by the loss of participants
- 9. Characteristics of RCTs Statistical methods used to compare groups • Number Needed to treat – Risk Difference (Absolute Risk Reduction) • Relative Risk • Odds Ratio
- 10. Characteristics of RCTs Statistical methods used to compare groups • Number Needed to treat 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 What proportion had inflammation in GingiFree group? 4 out of 55 or 7.3% This is called: Experimental Event Rate (EER) or Risk
- 11. Characteristics of RCTs Statistical methods used to compare groups • Number Needed to treat 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 What proportion had inflammation in placebo group? 14 out of 52 or 26.9% This is called: Control Event Rate (CER) or Risk
- 12. Characteristics of RCTs Statistical methods used to compare groups • Number Needed to treat 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 What is the difference in risk of inflammation between the two groups? CER – EER = ARR (Absolute Risk Reduction) 26.9% - 7.3% = 19.6
- 13. Characteristics of RCTs Statistical methods used to compare groups • Number Needed to treat 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 How many people do you need to treat with GingiFree to prevent 1 additional inflammation? Number Needed to Treat (NNT) 1 / ARR
- 14. Characteristics of RCTs Statistical methods used to compare groups • Number Needed to treat 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 How many people do you need to treat with GingiFree to prevent 1 additional inflammation? Number Needed to Treat (NNT) = 1/ARR 1 / 19.6 = 5.1
- 15. Characteristics of RCTs Statistical methods used to compare groups 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 What is the risk of developing inflammation in the experimental group relative to the control group? EER/CER = Relative Risk (Risk Ratio) 7.3/ 26.9 = 0.27
- 16. Characteristics of RCTs Statistical methods used to compare groups 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 What is the Odds Ratio of the study? Odds = 4/51 = 0.078 and 14/38 = 0.368 Odds Ratio = Odds of exp/Odds of control = 0.078/0.368 = 0.21
- 17. Critical Appraisal of the Evidence • What are the results? – How large was the treatment effect? • Relative risk, mean difference, etc. – How precise was the estimate of the treatment effect? • Confidence intervals
- 18. Critical Appraisal of the Evidence • Can I apply the results locally? – Can the results be applied to my patients? – Were all clinically important outcomes considered? – Are the likely treatment benefits worth the potential harms and costs?
- 21. The Basics of Critical Appraisal Critical Appraisal of RCTs Randomization The process of randomly allocating participants into one of the arms of a controlled trial. - tossing a coin - computer generated tables It assures: all factors are equal less bias in patient selection
- 22. The Basics of Critical Appraisal Critical Appraisal of RCTs Randomization Allocation concealment The process of preventing foreknowledge of group assignment in a randomized controlled trial. The most common method of concealment is the use of opaque, sealed envelopes.
- 23. The Basics of Critical Appraisal Critical Appraisal of RCTs Randomization Allocation concealment Blinding The process of preventing those involved in a trial from knowing to which comparison group a particular participant belongs.
- 24. The Basics of Critical Appraisal Critical Appraisal of RCTs Randomization Allocation concealment Blinding Intention to treat analysis Analysis by which all participants are included in the arm to which they were allocated, whether or not they received (or completed) the intervention given to that arm. Intention-to-treat analysis prevents bias caused by the loss of participants
- 25. The Basics of Critical Appraisal Critical Appraisal of RCTs 107 patients (30-40 years old) with mild periodontitis GingiFree Placebo No Inflammation 51 38 Inflammation 4 14 What is the odds of inflammation in the GingiFree group relative to placebo? Odds 4/51= 0.07 14/38=0.37 Odds Ratio = 0.07/ 0.37= 0.23