Combining first and second trimester markers for Down syndrome screening: Think twice
Article first published online: 22 OCT 2008
© 2008 The Authors. Journal compilation © 2008 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists
Australian and New Zealand Journal of Obstetrics and Gynaecology
Volume 48, Issue 5, pages 492–500, October 2008
How to Cite
COCCIOLONE, R., BRAMELD, K., O’LEARY, P., HAAN, E., MULLER, P. and SHAND, K. (2008), Combining first and second trimester markers for Down syndrome screening: Think twice. Australian and New Zealand Journal of Obstetrics and Gynaecology, 48: 492–500. doi: 10.1111/j.1479-828X.2008.00911.x
- Issue published online: 22 OCT 2008
- Article first published online: 22 OCT 2008
- Received 14 February 2008; accepted 13 April 2008.
- Down syndrome;
- integrated contingent;
- first trimester screening
Aims: This study compares different screening strategies for the detection of Down syndrome and considers practical implications of using multiple screening protocols.
Methods: The performance characteristics of each screening strategy were assessed based on datasets of Down syndrome (n = 11) and unaffected pregnancies (n = 1006) tested in both first and second trimester, as well as data from first trimester (n = 18 901) and second trimester (n = 40 748) pregnancies.
Results: For a detection rate of 91%, the false positive rates for integrated and serum integrated screening were 2.5% and 6.3%, respectively, compared with combined first trimester (4.6%) and second trimester (12.6%) screening. Contingent and sequential screening protocols achieved detection rates of 82 to 91% with false positive rates between 2.6 and 2.9%. Contingent protocols require retesting of 15 to 20% of cases in the second trimester. Sequential and integrated protocols require retesting of 98 to 100% of cases in the second trimester. The various screening strategies did not always detect the same Down syndrome pregnancies.
Conclusions: Combining first and second trimester markers for Down syndrome screening better defines the at-risk population. However, integrated protocols complicate management of screening programs and may not be suitable as primary screening strategies. It may be a better use of resources to refine current first and second trimester programs through improved access and new markers. We therefore suggest thinking twice before embracing integrated population screening programs.