Completed Therapy Worksheet for Evidence-Based General Practice
Citation
Schoenen J, Jacquy J, Lenaerts M. Effectiveness of high-dose riboflavin in migraine prophylaxis. A randomised controlled trial. Neurology. 1998; 50: 466-70.
Are the results of this single preventive or therapeutic trial valid?
-
Was the assignment of patients to treatments randomised?
And was the randomisation list concealed?
Yes -
Were all patients who entered the trial accounted for at its conclusion?
And were they analysed in the groups to which they were randomised?
Yes.
1 patient was excluded from analysis for a protocol violation. -
Were patients and clinicians kept "blind" to which treatment was being received?
Yes - the trial used a placebo identical to the riboflavin -
Aside from the experimental treatment, were the groups treated equally?
Yes - again the use of placebo helped control co-intervention. -
Were the groups similar at the start of the trial?
Yes
Are the valid results of this randomised trial important?
Sample Calculations
| Occurrence of diabetic neuropathy | Relative Risk Reduction RRR |
Absolute Risk Reduction ARR |
Number Needed to Treat NNT |
|
|---|---|---|---|---|
| Usual Insulin Control Event Rate CER |
Intensive Insulin 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 pts |
95% Confidence Interval (CI) on an NNT
= 1 / (limits on the CI of its ARR)
= 
= 
= ±2.4%
Your Calculations
| < 50% improvement in migraine frequency at 3 months | Relative Risk Reduction RRR |
Absolute Risk Reduction ARR |
Number Needed to Treat NNT |
|
|---|---|---|---|---|
| CER | EER | (CER - EER)/CER | CER - EER | 1/ARR |
| 81% | 46% | 43% | 35% | 3 |
Can you apply this valid, important evidence about a treatment in caring for your patient?
Do these results apply to your patient?
-
Is your patient so different from those in the trial that its results can't help you?
My patient had been having 4 migraines per month, and had had migraines for several years and so fulfilled the criteria. -
How great would the potential benefit of therapy actually be for your individual patient?
She'd expect to reduce the frequency from 4 to about 2 per month. -
Method I: f
Risk of the outcome in your patient, relative to patients in the trial. expressed as a decimal: _____
NNT/F
= ___ /___
= (NNT for patients like yours)
Are your patient's values and preferences satisfied by the regimen and its consequences?
-
Do your patient and you have a clear assessment of their values and preferences?
Taking riboflavin once per day would be worth avoiding 2 migraines per month. -
Are they met by this regimen and its consequences?
Additional Notes
The reduction in migraine frequency appeared to develop over the 3 months. Patients should not expect an immediate reduction. Riboflavin is available as a sole ingredient (not as a multivitamin) but costs around $10 per month.