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Re: risk for down syndrome From: David Nyberg (nyberg@u.washington.edu) Mon Dec 2 15:31:25 2002 Messages sorted by: [ date ][ thread ][ subject ][ author ] Next message: Terry J. DuBose: "Re: Nasal bones: images" Previous message: Dianne Walkup: "Re: new case-- Joe" In reply to: Dave Berck: "Re: risk for down syndrome" based on work of Snjiders, lethality between 12 and 16 weeks is probably 10%, certainly no more than 15%. Dave Nyberg On Mon, 2 Dec 2002, Dave Berck wrote: > 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 > -- David Nyberg, MD 1229 Madison St, #1150 Seattle, WA 98104 206-386-6300 x 40438 fax 206 386-6316 Next message: Terry J. DuBose: "Re: Nasal bones: images" Previous message: Dianne Walkup: "Re: new case-- Joe" In reply to: Dave Berck: "Re: risk for down syndrome"

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