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Effect of interrupting prenatal Down syndrome screening due to a large nuchal translucency
Author(s) -
Wald Nicholas J.,
Bestwick Jonathan P.,
Huttly Wayne J.
Publication year - 2012
Publication title -
prenatal diagnosis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.956
H-Index - 97
eISSN - 1097-0223
pISSN - 0197-3851
DOI - 10.1002/pd.3881
Subject(s) - medicine , nuchal translucency , prenatal screening , down syndrome , nuchal translucency measurement , gestation , obstetrics , prenatal diagnosis , antenatal screening , gynecology , screening test , fetus , pregnancy , pediatrics , genetics , psychiatry , biology
Objective The aim of this study is to determine the effect of interrupting prenatal Down syndrome screening for women with large nuchal translucency (NT) measurements on the performance of combined and integrated tests. Design Distribution of large NT at 11–13 weeks of gestation was determined from a screening programme (204 982 pregnancies, 509 with Down syndrome). Monte Carlo simulation was used to estimate the effects of interrupting screening on the detection rate (DR) and false‐positive rate (FPR) in (i) the remaining women and (ii) all women. Results At 12 weeks of gestation, 28% of affected (76/275) and 0.4% of unaffected (389/107 386) pregnancies had an NT of ≥3.5 mm. Among the remaining women, for an 85% DR, combined test FPR was 7.2% with interpretation of screening but 4.1% without interruption (1.8% and 0.9% respectively for integrated test). Among all women (women who interrupted screening with an NT of ≥3.5 mm and a 1/150 risk cut‐off for others), the FPR was 0.1 and 0.2 percentage points higher for the same DR at 12–13 weeks compared with no interruption using the combined and integrated tests, respectively, and 0.3 and 0.7 percentage points higher at 11 weeks. Conclusion Interrupting combined or integrated screening is acceptable using an NT of ≥3.5 mm, but screening performance in screened women will seem less than expected. This should be taken into account when performing audits. © 2012 John Wiley & Sons, Ltd.