Robert,
I'm not sure why expressing the result as a difference of half a day is a
problem? When there is a clear interpretable natural unit (such as hospital
days, days of pain, walking distance, episodes of angina per week, etc),
then why not stick to that? Just because kilograms are a good scale for
weights, does it mean we have to express height, temperature, velocity, etc
in kilograms?
NNT was invented because absolute risk reduction is not a particularly
natural unit for most folk, and inverting it makes it much easier to
understand.
However, since people vary, maybe you'd like to express it both ways: the
natural unit and NNT - in which case the method was outlined in Dave
Sackett's email.
Best wishes,
Paul Glasziou
At 11:55 PM 1/4/99 +0000, Robert Davis wrote:
>Can one of the participants on this list point us to a good discussion
>on the proper 'framing' of NNT in the context of a continuous outcome
>measure.
>
>For example, a rather bright fellow has posed this question to me:
>Treatment "X" shortens the hospital stay for disease "Z" by 0.50
>hospital days. Is there a relevant way to present this that is roughly
>equivalent to a NNT?
>
>I thought, off hand, that this would be somewhat equivalent to
>suggesting that 2 children would have to be treated to 'save' one
>hospital day. Fundamentally this appears overly simplistic, but I would
>be interested in hearing how others might have dealt with this before.
>
>Thanks in advance,
>
>Robert L. Davis, MD, MPH
>Pediatric Evidence Based Program
>Department of Pediatrics
>University of Washington
>Seattle, WA , USA
>
Paul Glasziou
Social & Preventive Medicine,
Medical School, Herston Rd,
Herston Qld 4006,
AUSTRALIA
PH 61-7-33655427 FAX: 61-7-33655442
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