Hi all,
I'm not familiar with the language around NNT's. But
I am intrigued by the arguements I'm hearing, as a
mental health professional. I've often wondered about
the cost benefits of medication for people with
schizophrenia. If you look at clozapine, which can be
a wonderfully effective medication, yet has side
effects that include weight gain. For many this may
be an acceptable price to pay. But weight can be
central to self esteem, particularly for women. And
in people recovering from mental health issues self
esteem is crucial, in my experience , both to the
degree to which the symptomns such as hearing voices
and paranoia affect people, as well as their ability
to cope with them. Working with women with
schizophrenia on clozapine who also have a history of
eating disorders, and seeing the impact the weight
gain has on them, I have wondered in the past at what
point the medication becomes counter therapeutic. Any
thoughts?
Yours sincerely,
Steve.
---"Djulbegovic, Benjamin" <[log in to unmask]>
wrote:
>
>
> As I argued it at this group before and as we
described it elsewhere (for
> details see Cancer Control 1998;5:394-405; also at
>
http://www.moffitt.usf.edu/pubs/ccj/v5n5/article2.html
, Med Decision
> Making 1998;18:464
> ; Comp Biomed Res; or, see
>
http://www.hsc.usf.edu/~bdjulbeg/Programs/BR/br-java.htm
), normatively
> highest (maximum) NNT at which treatment is worth
administering in
> prophylactic setting is equal to:
> NNT<NNH or NNT<1/ R
> where R is risk of the treatment .
> For example, for a toxicity of 2%, the treatment
NNT has to be at most 50 to
> be worth administering the treatment, for a
toxicity of 4%, the NNT has to
> be at most 25, etc.
>
> If this condition is not satisfied, no NNT is "good
NNT".
>
> In the setting of selection of Rx1 vs Rx2, in order
to even consider the
> treatment Rx1 as opposed to the alternative
treatment Rx2, the following
> inequality must be satisfied:
>
> NNT1 <= 1/(R1 - R2 + 1/NNT2)
>
>
> This is not only normatively correct, but also
makes sense intuitively: we
> should not consider measures of treatment benefits
without consideration of
> other side of therapeutic coin (that is, treatment
harm).Again, as I wrote
> before, it is important to realize that same units
of benefits and harms are
> used when these calculations are performed.
>
> I am not aware of any normative model that
successfully integrated patients
> values with NNT, NNH or with any other EBM summary
measures of therapeutic
> effects (although, I should say that we are
currently working on one such
> model)
>
> Intertwined with this issue is the question of
"action threshold". I will
> try to illustrate it from perspective of ongoing
discussion of CVD risk and
> New Zealand tables for CVD. The tables use data
from Framingham Heart study.
> These tables suggest threshold for therapeutic
action if risk of CVD is
> 10-15% at 5yrs (NNT=25 for 5 years) (see:
> http://cebm.jr2.ox.ac.uk/docs/prognosis.html )
However, this treatment
> threshold appears to be quite arbitrary. As I
argued before, normatively
> this action threshold (AT) is equal to
>
> AT= NNT/NNH or AT=risk of treatment*NNT=treatment
> risk/(RRR*morbidity/mortality without Rx) (for
details see references
> provided above).
>
> We should treat if estimated risk of clinical event
(in this case, CVD) is
> above AT; conversely, we should withhold Rx if risk
of CVD is below AT. For
> example, package insert for pravastatin indicated
that at median treatment
> of 4.8 years, 0.10% of patients treated with
pravastatin developed elevation
> of AST as opposed to 0.03% of placebo treated
patients. This would amount
> roughly to NNH=1428. Using the action threshold
equation this means that we
> can consider treatment with statins if risk of CVD
exceeds >1.7% at 5 years
> (AT=25/1428). Even when I vary risk in sensitivity
analysis, I still obtain
> threshold for action, which is below recommended 2%
or 3% per year. It is
> not clear to me how current recommendations (for
treatment actions) have
> been derived. Can somebody care to comment?
(Cardiovascular medicine is not
> my field, and I am perhaps missing something here).
>
> (Incidentally, I developed a simple BASIC program
that integrates this
> threshold model with Framingham risk equations. If
anybody is interested in
> the program, I will be happy to send it to him/her.)
>
>
>
> hope this clarifies this issue
>
> ben d
>
> Benjamin Djulbegovic, MD
> Associate Professor of Medicine
> H. Lee Moffitt Cancer Center & Research Institute
> at the University of South Florida
> Division of Blood and Bone Marrow Transplant
> 12902 Magnolia Drive
> Tampa, FL 33612
>
> e-mail:[log in to unmask]
> http://www.hsc.usf.edu/~bdjulbeg/
> phone:(813)979-7202
> fax:(813)979-3071
>
> > -----Original Message-----
> > From: Takeo Saio [SMTP:[log in to unmask]]
> > Sent: Friday, March 05, 1999 5:32 PM
> > To: Amit Ghosh
> > Cc: [log in to unmask]
> > Subject: RE: What is a good number for NNT?
> >
> > Hello! That's very good question.
> >
> > I think the NNTs of 2-4 are for therapeutic usage
of drugs,and the NNTs
> > over 20 are for preventitive usage of drugs.
> > i.e. for acute condition,NNTs of 2-4:for chronic
condition,NNTs of over
> > 20.
> >
> >
> > > A question I have , is what is a good number
for NNT? Bandolier 12
> > >indicated that a NNT of 2-4 is suggestive of
good NNT ( i.e., ARR of
> > >0.25-0.50). However most the the RCT reported in
journal s NEJM, Annals
> > >etc have statistical significance however their
NNT are usually over 20,
> > >ie, finasteride for BPH( NNT= 30). I reckon one
of the disadvantages of
> > >NNT maybe that despite the NNT being over 20 ,
these patients may have
> > >significant improvement in quality of life and
other subjective issues.
> > >Or is the fact that NNT of 2-4 an over
enthusiastic expectation when it
> > >comes to a clinical response.I guess in the case
of chronic diseases
> > >with outcomes occurring over decades a NNT of 50
would be acceptable,
> > >however in other more acute conditions one would
consider a smaller
> > >number for NNT as desirable. Could the members
throw some additional
> > >light in the defining what is a good number for
NNT.
> > **********************************************
> > Saio,Takeo
> > ///////////////CHIAKI hospital,JAPAN/////////
> > e-mail;[log in to unmask]
> > **********************************************
> >
> >
> >
>
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