Brian - I believe your maths is basically correct regarding nnts for
mammography. For the group of women at lower risk than those in the trials
you base your calculations on, the NNTs will be higher. The great debate
over age and screening underplayed the NNTs.
Rod
Rod
> I have greatly enjoyed and learned from the NNT discussion that has been
>taking place here. It has provoked this question, and I wonder what you all
>say.
> Over about 7 years, regular mammography reduces breast cancer deaths with a
>NNT (NNS?) of about 2,500. Assuming one does mammograms every 2 years (an
>average of 3 1/2 mammograms over 7 years), can one say that the chance of
>preventing a breast cancer death for a single woman with a single mammogram is
>about 1 in 8,750?
> I am not sure if this a valid way of extending the NNT.
> Thanks to all for considering this.
>Cheers and Best Wishes,
>Brian
>...................................................................
>Brian Budenholzer, MD
>Director, Clinical Enhancement & Development
>Group Health Northwest
>CC18
>PO Box 204
>Spokane, WA 99210-0204
>USA
>[log in to unmask]
>509/ 838-9100 X 7393
>fax: 509/ 458-0368
>.......................................................................
Dr Rodney Jackson MBChB PhD FAFPHM
Associate Professor of Epidemiology
Head of Department
Dpt of Community Health, School of Medicine
University of Auckland
(Grafton Mews, 52-54 Grafton Rd)
Private Bag 92019, Auckland, New Zealand
Phone: +64 (0)9-3737599 ext 6343
Fax: +64 (0)9-3737503
e-mail: [log in to unmask]
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