Re: Ultrasound & Down's - Are We As Good As We Think?
From: Richard M. Roberts (gene@vol.com)
Wed Feb 28 20:43:24 2001
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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