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Re: risk for down syndrome From: Dave Berck (djberck@yahoo.com) Mon Dec 2 08:08:49 2002 Messages sorted by: [ date ][ thread ][ subject ][ author ] Next message: Allen Worrall: "Re: new case-- Joe" Previous message: art fougner, md: "Re: new case-- Joe" Next in thread: David Nyberg: "Re: risk for down syndrome" Reply: David Nyberg: "Re: risk for down syndrome" Problem with this approach is: 1) correlation between 1st tri free bhcg and second tri hcg, thus need to eliminate 1st tri free bhcg from likelihood ration, which can be done with nicolaides software 2) need to adjust for lethality of trisomy 21 from 1st to second trimester which I believe is somewhere in the neighborhood of 25% (maybe slightly less). -- Dave Berck, MD, MPH, RDMS --- R L Meisel <rmeisel@mac.com> wrote: > >le 29/11/02 9:22, Patrizia : > > > >> the question is: do you know how to calculate > the sequential risk? > > > >You need the likelihood ratio from NT, first > trimester serum screening and > >second trimester serum screening. > > > >To respect the BAYES' rule, you have to multiply > the pre test risk (1:411) > >by the 3 likelihood ratios to calculate the > post-test risk. > > > > I calculated these from the given numbers in the > original message and > the cumulative risk is 1/2977 > > -- > Best Wishes, > R L Meisel, MD > ===== David J. Berck, MD, MPH Next message: Allen Worrall: "Re: new case-- Joe" Previous message: art fougner, md: "Re: new case-- Joe" Next in thread: David Nyberg: "Re: risk for down syndrome" Reply: David Nyberg: "Re: risk for down syndrome"

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