Are the results of this single preventive or therapeutic trial valid?
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Was the assignment of patients to treatments randomised?
Was the randomisation list concealed?
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Was follow-up of patients sufficiently long and complete?
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Were all patients analysed in the groups to which they were randomised?
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Were patients and clinicians kept “blind” to treatment?
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Were the groups treated equally, apart from the experimental treatment?
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Were the groups similar at the start of the trial?
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Are the valid results of this randomized trial important?
SAMPLE CALCULATIONS
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Occurrence of diabetic neuropathy at 5 years among insulin-dependent diabetics in the DCCT trial
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Relative risk reduction (RRR)
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Absolute risk reduction (ARR)
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Number needed to treat (NNT)
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Usual insulin regimen control event rate (CER)
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Intensive insulin regimen experimental event rate (EER)
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CER – EER
CER
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CER-EER
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1/ARR
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9.6%
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2.8%
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9.6% - 2.8%
9.6%
= 71%
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9.6% - 2.8%
= 6.8%
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1/6.8%
= 15 patients
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95% CI *Þ
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4.4% to 9.2%
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11 to 23
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* 95% confidence interval (CI) on an NNT = 1/(limits on the CI of its ARR) =
YOUR CALCULATIONS
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Relative risk reduction (RRR)
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Absolute risk reduction (ARR)
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Number needed to treat (NNT)
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CER
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EER
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CER – EER
CER
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CER-EER
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1/ARR
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95% CI Þ
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Can you apply this valid, important evidence about therapy in caring for your patient?
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Do these results apply to your 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: f
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Risk of the outcome in your patient, relative to patients in the trial.
Expressed as a decimal: ______
NNT/f = ______ / ______ = ______
(NNT for patients like yours)
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Method II: 1/(PEER x RRR)
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Your patient’s expected event rate if they received the control treatment (PEER)
= ______
1/(PEERxRRR) = 1/________ = ______
(NNT for patients like yours)
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Are your patient’s values and preferences satisfied by the regimen and its consequences?
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Do your patient and you 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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