Performance of first-trimester combined test for Down syndrome in different maternal age groups: reason for adjustments in screening policy?

Abstract

OBJECTIVE: To evaluate the performance of the first-trimester combined test (FCT) in different maternal age groups and to discuss whether adjustments in screening policies should be made. METHODS: In this retrospective study data (n = 26 274) from a fetal medicine center on FCT (maternal age, fetal NT, free beta-human chorionic gonadotrophin, pregnancy-associated plasma protein-A) were studied. Results : 70.6% of cases was <36 years and 43% of the Down syndrome (DS) cases were detected in this age group. For women <36 years and advanced maternal age (AMA) women (>/=36 years) detection rate (DR) and false positive rate (FPR) were 94.5% and 4.1%, and 95.8% and 13.0%, respectively (cut-off 1:200). Lowering the cut-off showed an improved balance in DR and FPR. With increasing maternal age FPR and DR increased and odds of being affected given a positive result (OAPR) decreased. CONCLUSION: FCT is effective in women <36 and >/=36 years. The balance between FPR and DR is more favourable in women <36 years with comparable OAPR. Although FPR increases with increasing maternal age, performance of FCT in AMA women is more effective than screening based on maternal age alone. Lowering the cut-off to 1:100 in AMA women is suggested to improve screening performance. Routinely offering diagnostic testing to AMA women as a screening policy for the detection of DS seems not reasonable.