Improved performance of first-trimester combined screening for trisomy 21 with the double test taken before a gestational age of 10 weeks
Article first published online: 1 AUG 2008
Copyright © 2008 John Wiley & Sons, Ltd.
Volume 28, Issue 9, pages 839–844, September 2008
How to Cite
Kirkegaard, I., Petersen, O. B., Uldbjerg, N. and Tørring, N. (2008), Improved performance of first-trimester combined screening for trisomy 21 with the double test taken before a gestational age of 10 weeks. Prenat. Diagn., 28: 839–844. doi: 10.1002/pd.2057
- Issue published online: 26 AUG 2008
- Article first published online: 1 AUG 2008
- Manuscript Accepted: 16 JUN 2008
- Manuscript Revised: 6 JUN 2008
- Manuscript Received: 8 APR 2008
- first-trimester screening;
- trisomy 21;
- Down syndrome;
- double test;
- consecutive combined test
To evaluate if there is a performance difference in the combined screening for trisomy 21 between the double tests performed before and after 10 + 0 weeks of gestation.
The study included all 97 trisomy 21 cases from January 2004 to December 2007, in a screening program where the double test was measured in week 8 + 0 to 13 + 6 and the nuchal translucency in week 11 + 3 to 13 + 6.
As many as 87 of the 97 cases were diagnosed in the screening program (detection rate = 90%). Among the 53 cases having the double test taken before 10 + 0 weeks, no cases were missed [detection rate (DR) = 100%, CI = 0.94–1.00] and among the 44 having the double test taken after 10 + 0 weeks, 10 cases were missed (DR = 77%, CI = 0.65–0.90). This difference in DR was highly significant (P = 0.0009). No difference was observed between false positive rates or median maternal age of the two groups.
A significantly higher DR was obtained when the double test was taken early in pregnancy (<10 + 0 weeks), than when it was taken later (≥10 + 0 weeks). The results could not be explained by a difference in either the false positive rate or the maternal age between the two groups. Copyright © 2008 John Wiley & Sons, Ltd.