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Re: 'Terrifying Sonogram' Dilemma: patient with single (new) 'softFrom: David Nyberg (nyberg@u.washington.edu)Fri May 23 11:16:57 2003
The nasal bone is a "soft" marker and fulfills some of the same criteria as other markers - it is not inherently significant itself, ie it carries not morbidity or mortality. It cannot be equated with a cardiac defect or omphalocele. - the marker (hypoplastic nasal bone) may be observed in normal fetuses but is more likely in aneuploid fetuses. It carries an inherent likelihood ratio. The question is, what is the likelihood ratio (risk)? As with other markers, there are other variables to consider. The likelihood ratio is considerably lower in African-Caribbean populations because of the higher false positive rate. Gestational age is undoubtedly a factor since the nasal bone is more likely not to be visible early (10-12 weeks) than later (13-14 weeks). The orientation of the fetus and the angle of the scan make a big difference. Factors of ethnicity, gestational age, and orientation of the fetus also affect the marker of echogenic intracardiac foci. The only real difference is the likelhood ratio is much less for EIF and may not be significant once we account for all other factors, including the nasal bone during the second trimester. In the first trimester, current estimates of LR for absent nasal bone may range as much as 10-40 depending on some of these factors. It may be high, but it is still a nonspecific marker. On Fri, 23 May 2003, Dave Berck wrote:
> Nicolaides Lancet paper about 18 months ago describes
-- David Nyberg, MD 10401 E McDowell Mtn Ranch Rd #2-372 Scottsdale, AZ 85255 ph 480-797-0993 fax 480-513-7765 work 480-425-5000
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