Re: Ultrasound & Down's - Are We As Good As We Think?
From: Mary Scarboro (oneiota@bellsouth.net)
Wed Feb 28 22:03:26 2001
Are they trying to say that in a group of 6819 high risk gestations (I
assume they mean advanced maternal age) with identified increased nuchal
folds, only one Down Syndrome would be culled? I can not even comprehend how
they came up with this number and in a metaanalysis study no less. Did they
happen to mention what criteria was used to identify 'high risk' or nuchal
fold?
Mary C Scarboro
-----Original Message-----
From: Richard M. Roberts <gene@vol.com>
To: Multiple recipients of list ULTRASOUND
<ultrasound@mail.medispecialty.com>
Date: Wednesday, February 28, 2001 10:33 PM
Subject: Re: Ultrasound & Down's - Are We As Good As We Think?
>Art--be not dismayed. Any metaanalysis utilizing data as old as 1980 is
>absurd, and not worth 2 cents. My take: this analysis has value only in
>adding a publication to the authors' CV, climbing up the ladder to full
>professor.
>
>At Wed, 28 Feb 2001, art fougner, md wrote:
>>
>>this in this week's JAMA
>>
>>Second-Trimester Ultrasound to Detect Fetuses With Down Syndrome
>>
>>A Meta-analysis
>>
>>Rebecca Smith-Bindman, MD; Wylie Hosmer, BS; Vickie A. Feldstein, MD;
>>Jonathan J. Deeks, MSc; James D. Goldberg, MD
>>
>>Context Second-trimester prenatal ultrasound is widely used in an
>>attempt to detect Down syndrome in fetuses, but the accuracy of this
>>method is unknown.
>>
>>Objective To determine the accuracy of second-trimester ultrasound in
>>detecting Down syndrome in fetuses.
>>
>>Data Sources English-language articles published between 1980 and
>>February 1999 identified through MEDLINE and manual searches.
>>
>>Study Selection Studies were included if they recorded second-trimester
>>findings of ultrasonographic markers, chromosomal abnormalities, and
>>clinical outcomes for a well-described sample of women. A total of 56
>>articles describing 1930 fetuses with Down syndrome and 130 365
>>unaffected fetuses were included.
>>
>>Data Extraction Articles were independently reviewed, selected, and
>>abstracted by 2 reviewers. Discrepancies in data abstraction were
>>resolved by consensus with a third reviewer. Overall estimates of
>>sensitivity, specificity, and positive and negative likelihood ratios
>>were calculated for the following markers: choroid plexus cyst,
>>thickened nuchal fold, echogenic intracardiac focus, echogenic bowel,
>>renal pyelectasis, and humeral and femoral shortening. Results were
>>stratified by whether markers were identified in isolation or in
>>conjunction with fetal structural malformations.
>>
>>Data Synthesis When ultrasonographic markers were observed without
>>associated fetal structural malformations, sensitivity for each was low
>>(range, 1%-16%), and most fetuses with such markers had normal outcomes.
>>A thickened nuchal fold was the most accurate marker for discriminating
>>between unaffected and affected fetuses and was associated with an
>>approximately 17-fold increased risk of Down syndrome. If a thickened
>>nuchal fold is used to screen for Down syndrome, 15 893 average-risk
>>women or 6818 high-risk women would need to be screened for each case of
>>Down syndrome identified. For each of the other 6 markers, when
>>observed without associated structural malformations, the marker had
>>marginal impact on the risk of Down syndrome. Because the markers were
>>detected in only a small number of affected fetuses, the likelihood of
>>Down syndrome did not decrease substantially after normal examination
>>findings (none of the negative likelihood ratios were significant).
>>
>>Conclusions A thickened nuchal fold in the second trimester may be
>>useful in distinguishing unaffected fetuses from those with Down
>>syndrome, but the overall sensitivity of this finding is too low for it
>>to be a practical screening test for Down syndrome. When observed
>>without associated structural malformations, the remaining
>>ultrasonographic markers could not discriminate well between unaffected
>>fetuses and those with Down syndrome. Using these markers as a basis
>>for deciding to offer amniocentesis will result in more fetal losses
>>than cases of Down syndrome detected, and will lead to a decrease in the
>>prenatal detection of fetuses with Down syndrome.
>>
>>JAMA. 2001;285:1044-1055
>>
>>folks, in our neck of the woods, serum screening leaves much to be
>>desired as well. any thoughts?
>>
>>art
>>
>>--
>>art fougner, md
>>
>>A series of 1000 cases begins with but a single anecdote.
>>
>
>--
>Richard M. Roberts, PhD, MD, FACMG
>
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