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Centre for Evidence-
Based Medicine

Completed Therapy Worksheet for Evidence-Based Gastroenterology and Hepatology

Citation

Poynard T, Marcellin P, Lee SS, et al. Interferon a 2b and ribavirin increased the loss of HCV RNA in chronic hepatitis C. Lancet 1998;352:1426-32.

Are the results of this single preventive or therapeutic trial valid?

  1. Was the assignment of patients to treatments randomised?
    And was the randomisation list concealed?
    Yes
  2. 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
  3. Were patients and clinicians kept "blind" to which treatment was being received?
    Yes, the trial was placebo controlled.
  4. Aside from the experimental treatment, were the groups treated equally?
    Yes
  5. Were the groups similar at the start of the trial?
    Yes

Are the valid results of this randomised trial important?

Sample Calculations

Virological presence at 6 months post treatment Relative Risk Reduction
RRR		 Absolute Risk Reduction
ARR		 Number Needed to Treat
NNT
Interferon alone
Control Event Rate
CER		 Interferon + ribavirin
Experimental Event Rate
EER		 (CER - EER)/CER CER - EER 1/ARR
80.7% 57.4% (80.7% - 57.4%)/80.7%
= 28.8%		 80.7% - 57.4%
= 23.3%		 1/23.3%
= 4.3 pts

95% Confidence Interval (CI) on an NNT
= 1 / (limits on the CI of its ARR)
= +-1.96 sqrt(((CERx(1-CER))/(# of control pts.)) + ((EERx(1-EER))/(# of exper. pts.)))
= 7.4%

Your calculations

Relative Risk Reduction
RRR		 Absolute Risk Reduction
ARR		 Number Needed to Treat
NNT
CER EER (CER - EER)/CER CER - EER 1/ARR
.81 .57 .29 .24 4

Can you apply this valid, important evidence about a treatment in caring for your patient?

Do these results apply to your patient?

  1. Is your patient so different from those in the overview that its results can't help you?
    no, this patient is similar

How great would the potential benefit of therapy actually be for your individual patient?

  1. Method I: f
    Risk of the outcome in your patient, relative to patients in the trial (expressed as a decimal): 1

    NNT/F
    = 4/1
    = 4 (NNT for patients like yours)
  2. Method II: 1 / (PEER x RRR)
    Your patient's expected event rate if they received the control treatment: PEER:______

    1 / (PEER x RRR)
    = 1/________
    = _______(NNT for patients like yours)

Are your patient's values and preferences satisfied by the regimen and its consequences?

  1. Do your patient and you have a clear assessment of their values and preferences?
    Needs to be assessed in each patient
  2. Are they met by this regimen and its consequences?
    Needs to be assessed in each patient

Additional Notes

-

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