Francesca Romana Grati,1* Andrea Barlocco,1 Beatrice Grimi,1 Silvia Milani,1 Giuditta Frascoli,1 Anna Maria Di Meco,1 Rosaria Liuti,1 Anna Trotta,1 Sara Chinetti,1 Francesca Dulcetti,1 Anna Maria Ruggeri,1 Simona De Toffol,1 Maurizio Clementi,2 Federico Maggi,1 and Giuseppe Simoni1
1Ricerca e Sviluppo, Citogenetica e Biologia Molecolare, TOMA Advanced Biomedical Assays S.p.A., Busto Arsizio, Varese, Italy
2Genetica Clinica, Dipartimento di Pediatria, Universit_a di Padova, Padova, Italy
Am J Med Genet A. 2010 Jun;152A(6):1434-42
During the past 20 years non-invasive screening tests have been increasingly utilized in prenatal diagnosis (PD) practice. Considerable effort has been exerted by multicenter consortia to evaluate the reliability of non-invasive screening tests in detecting those women with an increased risk of having a pregnancy affected by trisomies 21, 18, and 13, monosomy X, and triploidies. To what extent this group of abnormal karyotypes accounts for the total number of phenotypically relevant fetal chromosome abnormalities has, however, never been investigated. The present report is an attempt aimed to quantify this proportion.A retrospective analysis of a homogeneous survey of 115,128 consecutive invasive prenatal tests was undertaken. All cases were classified in accordance with the indication given for the invasive testing. Cytogenetic results regarding 96,416 karyotype analyses performed because of advanced maternal age (_35 years) or gestational anxiety (<35 years) were considered since these are the patients who usually undergo non-invasive screening tests. We calculated the number of cases (T21, T18, T13, 45,X, and triploidy) that would have been detected by prenatal screening onthe basis of the published detectionrate of the combined-2 test or the quadruple test. Our findings indicate that the chromosomal abnormalities investigated by screening tests represent <50%of the fetalchromosomal abnormalities associated with an abnormal outcome ranging from intermediate-to-severe in women <35 years (45.8% and 39.6% in the first and second trimesters, respectively), and sensitivity >50% in women _35 years (65.1% and 61.8%, respectively). To conclude, approximately 50% of the phenotypically relevant abnormal karyotypes cannot be detected by non-invasive prenatal screening tests. _ 2010 Wiley-Liss, Inc.
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