Embed Size (px)
DESCRIPTION
Forest plot
Citation preview
Understanding evidence: The big picture
Systematic reviews are the best way to understand the effects of treatments because they consider all the relevant, reliable evidence.
These slides will teach you how to interpret the main graph used to present the results of a systematic review of randomized trials.main graph
Main Graph
Relative Risk (RR)
Trial 1+2+3 +4+5+6+7
Trial 2
Trial 3
Trial 1
Trial 5
Trial 6
Trial 7
Trial 4
Favours Comparator BFavours Treatment AForest Plot
Many similar trialsMany similar trials
Steroids given before preterm delivery reduce the number of babies who die.
0.01
"No difference"RR=1
Favours placebo
Relative Risk (RR) of Death 0.1 0.5 1 102
10% die with steroid 5% die with placebo
RR = ??
10% die with steroid 5% die with placebo
RR = ??
5% die with steroid10% die with placebo
RR = ??
5% die with steroid10% die with placebo
RR = ??
10% die with steroid10% die with placebo
RR = ??
10% die with steroid10% die with placebo
RR = ??
Favours steroid
Relative Risk (RR) of death
0.01
Favours placebo
Relative Risk (RR) of Death 0.1 0.5 1 102
6.8%
11.2%
DeathsSteroid Placebo
6.8% 11.2%
Deaths
#1
Trial
= 0.61= 0.61
Babies
1070
Favours steroid
Relative Risk (RR) of death
Favours steroid
0.01
Favours placebo
Relative Risk (RR) of Death 0.1 0.5 1 102
95% Confidence interval"truth probably in here"
Point estimate"best guess at truth"Steroid Placebo
6.8% 11.2%
Deaths
#1
TrialBabies
1070
Relative Risk (RR) of death
0.01
Favours placebo
Relative Risk (RR) of Death 0.1 0.5 1 102
Steroid Placebo
6.8% 11.2%
Deaths
#1
TrialBabies
1070
#2 1.4% 8.2%130
#3 3.0% 11.9%126
#4 9.0% 10.0%127
#5 1.4% 6.7%
#6 2.5% 15.9%
#7 9.7% 10.0%
146
144
743
24862486TotalTotal
Relative Risk (RR) of death
Favours steroid
0.1 0.5 1 102
0.1 0.5 1 102
"Cumulative Meta-analysis"1972 36 60
1977
Placebo
DeathsSteroid
How long did it take to change practice?
Another decade and 10 more trials!
Favours placeboFavours steroidsYear
Relative Risk (RR) of Death
1070
37 651200
1978 39 721326
1979 44 79
1979 45 84
1980 47 94
1981 83 131
1453
1599
1743
2486
Babies
