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Apologies for long quote below. One of the problems with NNT is in defining the time period and costs. For example cardiovascular risks and risk reductions are usually calculated for periods of one or five years. If you calculate your NNTs from that point it is obvious that NNTs for young hypertensives to prevent a stroke or MI in five years are going to be large - so one could deduce that there is little benefit in treating a 40 year old man with BP 165/100, say, in terms of risk reduction over five years (the tables are not to hand so I'm not going to give an exact figure but it must be close to or over 100). And conversely there is a low NNT for treating an 80 year old (but the benefit of this is contradicted by the 80 year old's low life expectation compared to a 40 year old). What I'd really like to know is what is the NNT to prevent CVD in my 40 year old given a time scale of 15 or 20 years? That's when my hypertensive 40 year old will be 50-55 and at much higher risk of CVD. Is it worth starting treatment at the age of 40 compared to 45 or 50 in order to reduce the risk of adverse events when he is 55 or 60? Toby >There is no generic "good" NNT. It is completely dependent on: 1. the >value of the outcome you are trying to modify by treatment; 2. by the NNH >(ie the nummber need to harm) which you have to balance against the NNT; 3. >the costs of the treatments and the harms; and 4. the time period of >treatment, and time to benefit or harm. With respect to quality of life, >these are outcomes which can also be described in terms of NNTs and NNHs > >Rod Jackson > >>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. >>********************************************** -- Toby Lipman 7, Collingwood Terrace, Jesmond, Newcastle upon Tyne. Tel 0191-2811060 (home), 0191-2437000 (surgery) %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%