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Getting into the weeds a little more: Adding to Neal's and Andy's good points, I also think about the the 95% CI around an NNT, especially when the CI around the absolute difference is large (in this study, it was a five-fold diffference, 95% CI 5·1–24·9). The 95% CI would then be 4.1 - 19.0 for this NNT of 6.7. This range gives me an understanding of the precision of the estimate (not very good) and an NNT of 19 gives me a different feel than an NNT of 4.1. Similar calculations can be done for the natural frequencies. 

Allen


Allen F. Shaughnessy, Pharm.D., M.Med.Ed.
Director, Master Teacher Fellowship
Professor of Family Medicine
Tufts University School of Medicine
195 Canal Street
Malden, MA 02148
781-338-0507

On Thu, Jun 14, 2018 at 8:33 AM, Neal Maskrey <[log in to unmask]> wrote:

On days 14–42, and on average:

·         With hormonal therapy alone, 43 infants in 100 had spasms and 57 did not

·         With hormonal therapy plus vigabatrin, 28 infants in 100 had spasms and 72 did not


Thanks Andy! The key words being "on average’ because of course it isn’t possible to say in advance whether an individual child will be better with one treatment or the other, or be helped with neither, or whether one, or both treatments may make things worse or even harm that individual. We do seem to be seeing a collective recognition that there is a huge difference between decision making for an individual and the evidence for a population. Both are needed of course, but the population-based evidence can only inform individual decision making, and does not dictate a policy to be applied to everyone, everywhere, all of the time. Modern decision making in medicine is steadily progressing towards consultations being a skilled, nuanced negotiation involving but not dominated by information - which is itself necessarily balanced by its validity and relevance (themselves involving some careful judgements).

Great example Rohini. Thank you for posting. 

Best to all

Neal
Neal Maskrey
Visiting Professor of Evidence-informed decision making, Keele University
ADVOCATE Field Studies, University of Amsterdam; a Horizon 2020 European Oral Health Project  www.advocateoralhealth.com
Mobile: 07976276919











On 14 Jun 2018, at 13:18, Andy Hutchinson <[log in to unmask]> wrote:

On days 14–42, and on average:
·         With hormonal therapy alone, 43 infants in 100 had spasms and 57 did not
·         With hormonal therapy plus vigabatrin, 28 infants in 100 had spasms and 72 did not


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