Incorporación del estudio de ADN fetal en sangre materna al cribado de cromosomopatías / Incorporation of the study of fetal DNA in maternal blood to the screening of chromosomal diseases

OBJETIVO: Evaluar la efectividad del cribado combinado de primer trimestre para la detección prenatal de aneuploidías tras 6 años de implantación en nuestro servicio y su repercusión en la disminución de pruebas diagnósticas invasivas. Se propone establecer un protocolo para incorporar el estudio de ADN fetal en sangre materna a partir de las revisiones bibliográficas publicadas. MÉTODO: Se evaluó el riesgo de anomalía cromosómica fetal en 3177 gestaciones mediante cribado combinado de primer trimestre entre enero de 2011 y diciembre de 2014. Se revisaron las amniocentesis realizadas desde que se instauró el cribado combinado en 2008 comparándolas con las de los 5 años anteriores. RESULTADOS: La tasa de detección del cribado para trisomía 21 fue del 94,4% y la tasa de falsos positivos de 6,4%. En el año 2005 estábamos realizando 194 amniocentesis, tras 6 años de implantación del cribado, en el año 2013 se realizaron 35 amniocentesis lo que implica una disminución del 70%. CONCLUSIONES: El cribado combinado de primer trimestre ha demostrado una mayor tasa de detección para trisomía 21 que el cribado de segundo trimestre y/o la edad materna, además de que ha llevado a una importante reducción en el número de pruebas invasivas. En los próximos años la incorporación del estudio de ADN fetal mejorará la detección de aneuploidías, con una drástica disminución de las pruebas invasivas por lo que se hace necesario la implantación de nuevos protocolos.

AIMS: To evaluate the effectiveness of first trimester combined screening in the prenatal detection of aneuploidy after 6 years of implantation in our service and its impact in reducing invasive diagnostic tests. It is proposed to establish a protocol to incorporate the study of fetal DNA in maternal blood from published literature reviews. METHODS: The risk of fetal chromosomal anomalies was assessed in 3177 pregnancies with first trimester combined screening between January 2009 and December 2014. The amniocenteses performed were checked against those of the previous 5 years. RESULTS: The detection rate of screening for trisomy 21 was 94.4% and the false-positive rate was 6.4%. In 2005 there were 194 amniocenteses. In 2013, 5 years after the introduction of screening, 68 amniocenteses were performed, representing a 70% reduction in invasive procedures. CONCLUSIONS: First trimester combined screening has shown a higher detection rate for trisomy 21 that the second trimester screening and/or maternal age, and has substantially reduced the use of invasive prenatal diagnostics procedures. In the coming years, the incorporation of the study of fetal DNA improve the detection of aneuploidys with a drastic reduction of invasive tests so that, the implementation of new protocols is necessary.

Ultrasound Screening for Fetal Down Syndrome in the Second Trimester of Pregnancy / 대한산부인과학회잡지

OBJECTIVE: To determine the risk of Down syndrome in fetuses with sonographic markers using the likelihood ratios and individual risk assessment. METHODS: We retrospectively evaluated the midtrimester genetic sonographic features of fetuses with Down syndrome and compared them with euploid fetuses. Patients were referred for an increased risk of aneuploidy and evaluated for the presence of structural defects, a nuchal fold, short long bones, pyelectasis, brachycephaly, small stomach, and hyperechoic bowel. Outcome information included the results of genetic amniocentesis (if performed), the results of pediatric assessment, and follow-up after birth. The sensitivity, specificity, and likelihood ratios for markers ware calculated isolated findings. RESULTS: There were 59 fetuses with Down syndrome and 600 euploid fetuses. The presence of any marker resulted in sensitivity for the detection of Down syndrome of 86.4% with a false-positive rate of 13.6%. Structural defect had a likelihood ratio of 77.8. As an isolated marker, the nuchal fold, short humerus, short femur, echogenic bowel and renal pyelectasia has a likelihood ratio of 20.2, 12.7, 3.9, 2.5, 1.1 respectively. Other isolated markers had low likelihood ratios because of the higher prevalence in the unaffected population. CONCLUSION: Combining second-trimester serum testing and fetal sonography is a feasible approach to Down syndrome screening, compatible with current obstetric practice. Although an isolated marker with a low likelihood ratio may not increase a patient's risk of Down syndrome, the presence of such a marker precludes reducing the risk of aneuploidy. This information will be useful in counseling pregnant women who are at high risk for fetal Down syndrome and who prefer to undergo genetic sonography before deciding about genetic amniocentesis.

Ultrasound Screening for Fetal Down Syndrome in the Second Trimester of Pregnancy / 대한산부인과학회잡지

OBJECTIVE: To determine the risk of Down syndrome in fetuses with sonographic markers using the likelihood ratios and individual risk assessment. METHODS: We retrospectively evaluated the midtrimester genetic sonographic features of fetuses with Down syndrome and compared them with euploid fetuses. Patients were referred for an increased risk of aneuploidy and evaluated for the presence of structural defects, a nuchal fold, short long bones, pyelectasis, brachycephaly, small stomach, and hyperechoic bowel. Outcome information included the results of genetic amniocentesis (if performed), the results of pediatric assessment, and follow-up after birth. The sensitivity, specificity, and likelihood ratios for markers ware calculated isolated findings. RESULTS: There were 59 fetuses with Down syndrome and 600 euploid fetuses. The presence of any marker resulted in sensitivity for the detection of Down syndrome of 86.4% with a false-positive rate of 13.6%. Structural defect had a likelihood ratio of 77.8. As an isolated marker, the nuchal fold, short humerus, short femur, echogenic bowel and renal pyelectasia has a likelihood ratio of 20.2, 12.7, 3.9, 2.5, 1.1 respectively. Other isolated markers had low likelihood ratios because of the higher prevalence in the unaffected population. CONCLUSION: Combining second-trimester serum testing and fetal sonography is a feasible approach to Down syndrome screening, compatible with current obstetric practice. Although an isolated marker with a low likelihood ratio may not increase a patient's risk of Down syndrome, the presence of such a marker precludes reducing the risk of aneuploidy. This information will be useful in counseling pregnant women who are at high risk for fetal Down syndrome and who prefer to undergo genetic sonography before deciding about genetic amniocentesis.