Hi Steve,
I think this is a great example of where Sharon Straus' way of looking at
the likelihood of being helped or harmed can be so useful. This allows a
patient to come to a choice about a treatment taking into account the
probability of both good and adverse outcomes - weighted according to the
patient's own views on how they rate the desirability or otherwise of these
outcomes.
Cheers
john
At 12:48 09/03/99 -0800, stephen thayne wrote:
>
>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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