OP01.06: Stepwise sequential screening for Down syndrome at a referral centre in Prague, Czech Republic

Abstract

To evaluate the efficiency of individual segments of the three part step-wise sequential screening for Down syndrome (DS) in an unselected population. We reviewed the cytogenetic results of 7434 pregnancies tested by sequential test at our center between October 2002 and December 2007. Test consisted of three parts: 1/combined test in the first trimester with DS risk cutoff 1/100 and CVS offer at positive cases 2/all first trimester negative continued without published DS risk and their results were integrated with the second trimester part (triple test) with risk cutoff 1/250 and AMC offer at positive cases. 3/All continuing mothers were scanned in the 20th week Pre and post natal cytogenetic results of this group were retrieved from our laboratory information system. The mean maternal age was 37.7 years with 20% mothers over 35 years. Crude detection rate was 50/52 (96%). 41/52 (8.8%) of all DS cases were detected by first trimester combined test. 6/52 (11.5%) of DS cases were detected by second trimester integrated test. 1/52(1.8%) integrated screen negative cases were indicated to invasive prenatal diagnosis by results of second trimester scan and 2/52 (3.8%) of maternat age. Also 2/52 (3.8%) DS cases were born all test negative. False positive rate (FPR) of combined and integrated tests was 1.43%, respective 3.8%. 26/52 (50%) prenatal diagnoses was made by CVS. Step-wise sequential test is highly efficient with detection rate over 90% and acceptable false positive rate 6.5%. All segments are important with priority of first trimester combined test.