Dear Jon and all Listers,
Regarding Jon's query about the number treated needlessly (NTN) or the index
of therapeutic impotence (ITI) in Bogaty's article I have an opinion that I
want to discuss with you.
First, I only read the abstract but not the whole article but I find these
two new indices, as such, misleading. That's why Jon asks his question.
The NNT is the number of patients needed to be treated by a given treatment
to get one "MORE" benefit than another treatment, or a placebo, in the
So if 33 is the number needed to treat for a given drug "compared to
another" we can not say that we have 32 who failed to be treated with it so
that the NTN is 32 and the ITI is 97%!
We may have 32 patients who are treated successfully out of every 33
patients in the intervention group compared to 31 out of every 33 in the
control group. In this situation the NNT is 33 but the ITI (for the
intervention) is 1/33 which is 3% actually.
The same indices will change with the change of the numbers treated
successfully for the same NNT. If we have 17 patients treated successfully
out of every 33 patients in the intervention group compared to 16 out of
every 33 in the control group. In this situation the NNT is 33 but the ITI
is 16/33 which is 48.5%.
Any opinions on this?
Best of wishes,
Prof. Dr. Abdelhamid Attia
Prof. of Ob & Gyn, Cairo University
President; Arab Federation of EBM
Executive Director, Center of EBM, Cairo University
----- Original Message -----
From: "Jon Brassey" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, March 05, 2006 10:51 AM
Subject: Re: Best EBM methods papers for 2005?
> Dear All,
> I must thank Michael for bringing that Bogaty and Brophy article. I
haven't come across this article, or reference to it.
> Is anyone aware of this being discussed at great depth anywhere? Does
anyone have an opinion on it? From a patient perspective I wonder how the
interplay of 'most effective intervention' might fit with an ITI of 97% or a
NTN of 32.
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