Integrated Dentistry I Third Year

1. Randomized Controlled Trials
Part 2

2. Outcomes
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•
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