IONA test for first‐trimester detection of trisomies 21, 18 and 13

OBJECTIVE: To assess the potential performance of screening for fetal trisomies 21, 18 and 13 by cell‐free DNA (cfDNA) analysis of maternal blood using the IONA® test. METHODS: This was a nested case–control study of cfDNA analysis of maternal plasma using the IONA test. Samples were obtained at 11–13 weeks' gestation, before chorionic villus sampling, from 201 euploid pregnancies, 35 with trisomy 21, four with trisomy 18 and two with trisomy 13. Laboratory personnel were blinded to the fetal karyotype. RESULTS: Probability scores for trisomies 21, 18 and 13 were given for 241/242 samples analyzed. No probability score was provided for one (0.5%) euploid pregnancy because of low fetal fraction. In all 35 cases of trisomy 21 the probability score for trisomy 21 was > 95% and the scores for trisomies 18 and 13 were ≤ 0.0001%. In all four cases of trisomy 18, the probability score for trisomy 18 was > 77% and the scores for trisomies 21 and 13 were ≤ 0.0001%. In the two cases of trisomy 13, the probability score for trisomy 13 was > 59% and the scores for trisomies 21 and 18 were ≤ 0.0001%. In the 200 euploid pregnancies with a test result, the probability score was < 0.08% for trisomy 21, < 0.001% for trisomy 18 and < 0.002% for trisomy 13. Therefore, the IONA test detected 100% of all three trisomies, with a false‐positive rate of 0%. CONCLUSION: The IONA test successfully differentiated all cases of trisomies 21, 18 and 13 from euploid pregnancies. © 2015 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.