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trabalhos interessantes VIIIFrom: Jaime (jaimen@zaz.com.br)Thu, 8 Mar 2001 11:21:28 -0300
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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