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Effect on down syndrome screening performance of adjusting for marker levels in a previous pregnancy
Author(s) -
Wald Nicholas J.,
Barnes Isobel M.,
Birger Ruthie,
Huttly Wayne
Publication year - 2006
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.1455
Subject(s) - down syndrome , pregnancy , medicine , obstetrics , aneuploidy , trisomy , genetics , biology , psychiatry , gene , chromosome
Objectives In prenatal screening for Down syndrome, serum marker values can be adjusted using values from a previous pregnancy to avoid the problem of women having a high chance of recurrent false‐positive results. We investigate the effect of such adjustment on overall screening performance. Methods Monte Carlo simulation was used to investigate the effect of this adjustment on five widely used screening tests for Down syndrome (Triple, Quadruple, Combined, serum Integrated, Integrated tests). Results Adjustment for screening marker values (expressed in multiples of the median, (MoM)) in a previous pregnancy improved screening performance. The detection rate for a 1% false‐positive rate (FPR) increased from 54 to 59% with the Triple test, from 63 to 68% with the Quadruple test, from 71 to 75% for the Combined test, from 71 to 76% for the serum Integrated test, and from 85 to 88% for the Integrated test. The FPR for an 85% detection rate decreased from 10 to 7.9%, 7.1 to 4.9%, 4.9 to 3.7%, 4.7 to 2.9% and 1.1 to 0.7% respectively for the five tests. Among women who have had a false‐positive result in a previous pregnancy, adjustment substantially lowers the false‐positive rate, for example, from 19 to 7.3% with the Combined test using a 1 in 250 risk cut‐off. Conclusion MoM adjustment for values in a previous pregnancy improves overall screening performance and substantially reduces the high recurrent false‐positive rate. This adjustment can be routinely applied in screening programmes through the screening software used to interpret a woman's screening results. Copyright © 2006 John Wiley & Sons, Ltd.