Straus SE, Richardson WS, Glasziou P, Haynes RB. Evidence-based medicine: how to practice and teach EBM, 3nd ed. Elsevier Churchill Livingston: 2005. pp 115-143.
Kheirandish-Gozal L, Gozal D. Intranasal budesonide treatment for children with mild obstructive sleep apnea syndrome. Pediatrics 2008;122:e149-e155.
Are the results of this single preventive or therapeutic trial valid?
- Was the assignment of patients to treatments randomized?
- Was the randomization list concealed?
- Was follow-up of patients sufficiently long and complete?
- Were all patients analyzed in the groups to which they were randomized?
- Were patients, clinicians, and study personnel kept “blind” to treatment?
- Were the groups treated equally, apart from the experimental treatment?
- Were the groups similar at the start of the trial apart from the experimental therapy?
Are the valid results of this randomized trial important?
- What is the magnitude of the treatment effect?
- How precise is the estimate of the treatment effect?
SAMPLE CALCULATIONS
|
Occurrence of diabetic neuropathy at 5 years among insulin-dependent diabetics in the DCCT trial |
Relative risk reduction (RRR) |
Absolute risk reduction (ARR) |
Number needed to treat (NNT) |
||||
|
Usual insulin regimen control event rate (CER) |
Intensive insulin regimen experimental event rate (EER) |
CER – EER CER |
CER – EER |
1/ARR |
|||
| 9.6% | 2.8% |
9.6% – 2.8% 9.6% =71% |
9.6% – 2.8% =6.8% |
1/6.8% =15 patients |
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|
95% CIa |
4.4% to 9.2% |
11 to 23 |
|||||
a95% confidence interval (CI) on an NNT
=1/(limits on the CI of its ARR)
YOUR CALCULATIONS
|
|
Relative risk reduction (RRR) |
Absolute risk reduction (ARR) |
Number needed to treat (NNT) |
||||
|
CER |
EER |
CER – EER
CER |
CER – EER |
1/ARR |
|||
|
95% CI |
|||||||
Can you apply this valid, important evidence about theapy in caring for your patient?
- Do these results apply to our patient?
- Is our patient so different from those in the study that its results cannot apply?
- Is the treatment feasible in our setting?
- What are our patient’s potential benefits and harms from the therapy?
| Method I: f | Risk of the outcome in our patient, relative to patients in the trial.
Expressed as a decimal:______ NNT/f=______/______=______ (NNT for patients like ours) |
| Method II: 1/(PEER´RRR) | Our patient’s expected event rate if they received the control treatment (PEER)
=______ 1/(PEER´RRR)=1/________=______ (NNT for patients like ours) |
- Are our patient’s values and preference satisfied by the regimen and its consequences?
- Do we and our patient have a clear assessment of their values and preferences?
- Are they met by this regimen and its consequences?
Additional notes:
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