Re: 'Terrifying Sonogram' Dilemma: patient with single (new) 'soft
From: RBurns (bito02@aol.com)
Fri May 23 12:32:23 2003
This is part of the dilemma -- while the NT did not screen deliberately
for the nasal bone at 13wks, the sonogram itself seems to show a nasal
bone. The same is true at the 19wk Level II u/s. So the dilemma really
involves three things -- a) the accuracy of the 25wk Level I; and b)
what could account for the change b/w visible nasal bone at 19wks and
non-visible at 25wks other than sonographer error? and c) assuming the
abnormality of the nasal bone, how to calculate the ds risk in the
context of all of the other low risk variables?
By the way, have any studies on nasal bone development been done
regarding Asian fetuses? The patient's fetus is bi-racial
Caucasian/Filipino.
At Fri, 23 May 2003, David Nyberg 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
>
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