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Citation:
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Are the results of this systematic review valid?
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Is this a systematic review of randomised trials? |
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Does it include a methods section that describes: a) finding and including all relevant trials? b) assessing their individual validity? |
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Were the results consistent from study to study? |
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Were the individual patient data used in the analysis (or aggregate data)? |
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Are the valid results of this systematic review important?
Translating odds ratios to NNTs:
The numbers in the body of the tables are the NNTs for the corresponding odds ratio at that particular patient’s expected event rate (PEER).
1. When the odds ratio (OR) < 1
This table applies when a bad outcome is prevented by therapy.
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OR < 1 |
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0.9 |
0.8 |
0.7 |
0.6 |
0.5 |
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Patient’s expected event rate (PEER) |
0.05 |
2.09a |
104 |
69 |
52 |
41b |
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0.10 |
110 |
54 |
36 |
27 |
21 |
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0.20 |
61 |
30 |
20 |
14 |
11 |
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0.30 |
46 |
22 |
14 |
10 |
8 |
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0.40 |
40 |
19 |
12 |
9 |
7 |
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0.50 |
38 |
18 |
11 |
8 |
6 |
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0.70 |
44 |
20 |
13 |
9 |
6 |
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0.90 |
101c |
46 |
27 |
18 |
12d |
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a The relative risk reduction (RRR) here is 10%
b The RRR here is 49%
c For any OR, NNT is lowest when PEER = 0.50
d The RRR here is 9%
2. When the odds ratio (OR) > 1
This table applies both when a good outcome is increased by therapy and when a side-effect is caused by therapy.
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OR > 1 |
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1.1 |
1.2 |
1.3 |
1.4 |
1.5 |
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Patient’s expected event rate (PEER) |
0.05 |
212 |
106 |
71 |
54 |
43 |
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0.10 |
112 |
57 |
38 |
29 |
23 |
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0.20 |
64 |
33 |
22 |
17 |
14 |
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0.30 |
49 |
25 |
17 |
13 |
11 |
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0.40 |
43 |
23 |
16 |
12 |
10 |
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0.50 |
42 |
22 |
15 |
12 |
10 |
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0.70 |
51 |
27 |
19 |
15 |
13 |
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0.90 |
121 |
66 |
47 |
38 |
32 |
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Can you apply this valid, important evidence from a systematic review in caring for your patient?
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Do these results apply to our patient? |
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Is your patient so different from those in the study that its results cannot apply? |
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Is the treatment feasible in your setting? |
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What are your patient’s potential benefits and harms from the therapy? |
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Method I: In the OR tables above, find the intersection of the closest odds ratio from the systematic review and your patient’s expected event rate (PEER) |
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Method II: To calculate the NNT from any OR and PEER:
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Are your patient’s values and preferences satisfied by the regimen and its consequences? |
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Do you and you patient have a clear assessment of their values and preferences? |
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Are they met by this regimen and its consequences? |
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Should you believe apparent qualitative differences in the efficacy of therapy in some subgroups of patients?—Only if you can say ‘yes’ to all of the following:
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Do they really make biologic and clincal sense? |
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Is the qualitative difference both clinically (beneficial for some but useless or harmful for others) and statistically significant? |
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Was this difference hypothesised before the study began (rather than the product of dredging the data), and has it been confirmed in other, independent studies? |
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Was this one of just a few subgroup analyses carried out in this study? |
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