Re: 'Terrifying Sonogram' Dilemma: patient with single (new) 'soft marker' -- all other screens normal
From: Dave Berck (djberck@yahoo.com)
Tue May 27 15:48:53 2003
Thank you Dr. Nyberg. As concerns the nasal bone, if
the LR is as high as 40, wouldn't virtually any
patient with this finding, even those who may have
screened negative by 1st or 2nd trimester screening,
into the category of "screen positive," i.e. a T-21
risk above the traditional age-related risk of a 35
year old (about 1:270)? (I guess that's what I mean by
a "hard marker", although I appreciated the
distinction you have drawn between markers which are
themselves significant anomalies and those that are
not).
--- David Nyberg <nyberg@u.washington.edu> wrote:
> 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
> > the proper way to image the nasal bone in the 2nd
> > trimester. Like NT measurements, if you don't know
> > what you're doing, you'll definitely do a bad job.
> I
> > would suggest that there are few radiologists who
> have
> > any idea of how to measure a NB properly.
> >
> > Furthermore, the finding of a soft marker should
> not
> > cause you to throw the screening results out of
> the
> > window. You have to consider them in aggregate.
> >
> > Lastly, I would suggest that the finding of an
> absent
> > nasal bone is actually NOT a soft marker, but
> rather a
> > marker that greatly increases the risk of DS, more
> > along the lines of an AV Canal defect or
> omphalocele.
> >
> > Does anyone agree?
> >
> > --- RBurns <bito02@aol.com> wrote:
> > > This "may" communication is my error, not an
> error
> > > in the report. The
> > > actual report indicates that "they are concerned
> > > about the development
> > > of the nasal bone." In the original Level II
> u/s,
> > > the nasal bone appears
> > > present; in the subsequent Level I, it is
> absent.
> > > Thus, they are
> > > suggesting that there is something concerning
> about
> > > the development of
> > > the nasal bone itself.
> > >
> > > But I surely agree; Levels are only as good as
> the
> > > sonographers
> > > performing the screen --
> > >
> > > Does that clarify things?
> > >
> >
> > =====
> > David J. Berck, MD, MPH
> >
>
> 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
>
=====
David J. Berck, MD, MPH
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