The Integrated test combines results from first-trimester nuchal translucency (NT) measurement with first- and second-trimester serum hormone levels to screen for Down syndrome (DS) and the test has been offered routinely to women booking for antenatal care at our institution since January 2003. Our current policy is to offer immediate invasive testing to women with an NT ≥ 3.5 mm and we evaluated this policy for the first 3 years of Integrated test screening. This was a retrospective study of 8311 women booked for antenatal care at University College London Hospital who were screened for DS by the Integrated test. First-trimester sonogram reports and pregnancy outcomes were analyzed using an NT measurement cut-off of ≥ 3.5 mm. The NT measured ≥ 3.5 mm in 151 (1.8%) of the women screened; 131 women (87%) whose fetus had an NT ≥ 3.5 mm opted for immediate invasive testing by chorionic villus sampling (n = 130) or amniocentesis (n = 1). The remainder continued with screening by the combined test (n = 5) or the Integrated test (n = 3). There were 46 cases of DS in the screened population of which 30 had an NT ≥ 3.5 mm (detection rate 65%). There were 23 other aneuploidies with an NT ≥ 3.5 mm, including trisomy 13 (n = 12), trisomy 18 (n = 5) and Turner's syndrome (n = 6). The detection rate of the Integrated test at UCLH for DS was 90% with a false-positive rate of 2.3%. In women undergoing Integrated screening we detected a high proportion of DS fetuses and other aneuploidies in the first trimester, using a policy of offering an immediate invasive test when the NT measurement was ≥ 3.5 mm. The majority of women in this high-risk group had invasive testing, but the DR for the Integrated test remained high.
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