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Noninvasive prenatal testing in routine clinical practice – An audit of NIPT and combined first‐trimester screening in an unselected Australian population
Author(s) -
McLennan Andrew,
PalmaDias Ricardo,
Silva Costa Fabricio,
Meagher Simon,
Nisbet Debbie L.,
Scott Fergus
Publication year - 2016
Publication title -
australian and new zealand journal of obstetrics and gynaecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.734
H-Index - 65
eISSN - 1479-828X
pISSN - 0004-8666
DOI - 10.1111/ajo.12432
Subject(s) - medicine , trisomy , obstetrics , gynecology , prenatal diagnosis , population , aneuploidy , monosomy , cell free fetal dna , genetic testing , fetus , pregnancy , karyotype , chromosome , genetics , biology , environmental health , gene
Background There are limited data regarding noninvasive prenatal testing ( NIPT ) in low‐risk populations, and the ideal aneuploidy screening model for a pregnant population has yet to be established. Aims To assess the implementation of NIPT into clinical practice utilising both first‐ and second‐line screening models. Materials and Methods Three private practices specialising in obstetric ultrasound and prenatal diagnosis in Australia offered NIPT as a first‐line test, ideally followed by combined first‐trimester screening ( cFTS ), or as a second‐line test following cFTS , particularly in those with a calculated risk between 1:50 and 1:1000. Results NIPT screening was performed in 5267 women and as a first‐line screening method in 3359 (63.8%). Trisomies 21 and 13 detection was 100% and 88% for trisomy 18. Of cases with known karyotypes, the positive predictive value ( PPV ) of the test was highest for trisomy 21 (97.7%) and lowest for monosomy X (25%). Ultrasound detection of fetal structural abnormality resulted in the detection of five additional chromosome abnormalities, two of which had high‐risk cFTS results. For all chromosomal abnormalities, NIPT alone detected 93.4%, a contingent model detected 81.8% ( P = 0.097), and cFTS alone detected 65.9% ( P < 0.005). Conclusions NIPT achieved 100% T21 detection and had a higher DR of all aneuploidy when used as a first‐line test. Given the false‐positive rate for all aneuploidies, NIPT is an advanced screening test, rather than a diagnostic test. The benefit of additional cFTS was the detection of fetal structural abnormalities and some unusual chromosomal abnormalities.