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
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0.8
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0.7
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0.6
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0.5
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Patient’s expected event rate (PEER)
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0.05
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2.09a
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104
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69
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52
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41b
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0.10
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110
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54
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36
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27
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21
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0.20
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61
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30
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20
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14
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11
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0.30
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46
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22
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14
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10
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8
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0.40
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40
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19
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12
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9
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7
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0.50
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38
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18
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11
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8
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6
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0.70
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44
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20
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13
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9
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6
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0.90
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101c
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46
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27
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18
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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
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1.2
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1.3
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1.4
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1.5
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Patient’s expected event rate (PEER)
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0.05
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212
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106
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71
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54
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43
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0.10
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112
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57
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38
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29
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23
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0.20
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64
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33
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22
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17
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14
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0.30
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49
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25
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17
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13
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11
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0.40
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43
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23
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16
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12
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10
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0.50
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42
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22
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15
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12
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10
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0.70
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51
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27
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19
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15
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13
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0.90
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121
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66
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47
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38
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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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