OBSTET-L Mensagens pela Março, 2001: Re: trabalhos interessantes VIII

Re: trabalhos interessantes VIII

From: Thomaz Rafael Gollop

trgollop@usp.br

Sun, 11 Mar 2001 06:56:51 -0300

Prof. Thomaz Gollop

Jaime wrote:

> Aos colegas da lista
>
> Ultrasom para rastrear sindrome de Down é um método bastante pobre.
>
> Publicação em 28/02/2001 The Journal of the American Medical Association
> (JAMA)
>
> A Dra. Rebecca Smith e o Dr. Bindman, da Universidade da Califórnia, em São
> Francisco e seu grupo, realizaram uma meta análise de 56 estudos que
> avaliaram a ultrasonografia de segundo trimestre como método rastreador da
> sindrome de Down.
> Os trabalhos escritos encontraram 130.365 fetos saudáveis que tinham falso
> positivo para a sindrome cromossomial, contra 1.930 fetos realmente com a
> sindrome de Down
>
> Todos os estudos selecionaram mulheres com risco de gerar fetos com
> anomalias cromossomiais.
>
> Os marcadores ultrassonográficos usados, foram a prega nucal e o cisto de
> plexo coroide, aquela mais confiável que este. Calcularam 79 falso
> positivos para a prega nucal e 611 para o cisto de plexo coróide para cada
> caso de Down detectado.
>
> O problema é que cada caso suspeito invariavelmente parte para métodos
> invasivos e aí temos mais perdas de fetos saudáveis pelas complicações dos
> métodos invasivos do que diagnósticos de Down.
> Além disso a ansiedade imposta ao casal é imensurável, causando muito
> sofrimento até o nascimento do bebê.
>
> Mais detalhes
>
> Second-Trimester Ultrasonography Impractical Screening Test for Down
> Syndrome
>
> WESTPORT, CT (Reuters Health) Feb 27 - Second-trimester ultrasonography is a
> poor method of detecting fetuses with Down syndrome, resulting in more fetal
> losses than cases of the syndrome detected, according to a recently
> conducted meta-analysis of published studies.
>
> Dr. Rebecca Smith-Bindman, of the University of California, in San
> Francisco, and associates included in their analysis 56 studies that
> recorded second-trimester prenatal ultrasonographic markers reportedly
> associated with chromosomal abnormalities and outcome information. The
> articles described findings for 130,365 unaffected fetuses and 1930 fetuses
> with Down syndrome.
>
> The sensitivity for Down syndrome was low, though the specificity for each
> marker was >95%, the investigators report in The Journal of the American
> Medical Association for February 28. The most accurate marker for
> discriminating between unaffected and affected fetuses was a thickened
> nuchal fold, but even this marker had a low sensitivity.
>
> The investigators calculated that between 4454 and 87,413 women at average
> risk of having an affected fetus would need to be screened to detect one
> case of Down syndrome. False positives would range from 79 for nuchal fold
> to 611 for choroid plexus cysts for each case of Down syndrome detected.
>
> Dr. Smith-Bindman's team writes, "The use of the ultrasonographic markers as
> an indicator for invasive testing with amniocentesis will lead to an
> increase in the number of unaffected fetuses lost as a complication of the
> procedure."
>
> On the other hand, the investigators note, if women considered to be at risk
> on the basis of maternal age or serum testing results forego amniocentesis
> due to the absence of ultrasonographic markers, the prenatal detection of
> Down syndrome will actually be reduced.
>
> "Most physicians who I speak with don't really like using these markers,"
> Dr. Smith-Bindman told Reuters Health. "They don't believe they're helpful
> in identifying babies truly affected by Down syndrome. But in this
> medical-legal environment, they feel that once they've seen it they're
> compelled to explain it to the woman and therefore recommend invasive
> testing."
>
> This causes a huge amount of anxiety for women, Dr. Smith-Bindman noted.
> "Unfortunately, even when a second ultrasound or amniocentesis shows the
> baby is normal, women remain stressed about it until the end of pregnancy,"
> she said. "Women are concerned if they've been told, for example, that their
> baby had a cyst in the brain."
>
> JAMA 2001;285:1044-1055.
>
> Jaime Nonato http://www.jaimenonato.com jaimen@zaz.com.br
>

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