Objective: To develop a screening test for fetal trisomy 13, 18, and 21 using cell-free DNA from maternal blood with an automated workflow using the Ion Proton sequencing platform. Methods: An automated next-generation sequencing workflow was developed using the Ion Proton sequencing platform and software developed for straightforward bioinformatic analysis. An algorithm was developed using 239 samples to determine the likelihood of trisomy, using DNA fragment counts and a fetal fraction validity check; the results were compared with those from invasive diagnostic procedures. A further 111 samples were used to assess the tests' sensitivity (detection rate) and specificity (1 minus false-positive rate). Results: The 110 of a possible 111 valid samples used to verify the IONA® test gave 100% sensitivity and specificity, compared with invasive diagnostic procedures; one failed the fetal fraction validity check giving a sample failure rate of 0.29% across all 350 analysed samples. Conclusion: The data indicate that the IONA test provides a robust, accurate automated workflow suitable for use on maternal blood samples to screen for trisomies 13, 18, and 21. The test has the potential to reduce the number of unnecessary invasive procedures performed and facilitate testing by screening laboratories.

ObjectiveTo evaluate the clinical accuracy of the IONA® test for aneuploidy screening.MethodsThis was a multicenter blinded study in which plasma samples from pregnant women at increased risk of trisomy 21 underwent cell‐free DNA analysis utilizing the IONA test. For each sample, the IONA software generated a likelihood ratio and a maternal age‐adjusted probability risk score for trisomies 21, 18 and 13. All results from the IONA test were compared against accepted diagnostic karyotyping.ResultsA total of 442 maternal samples were obtained, of which 437 had test results available for analysis and assessment of clinical accuracy. The IONA test had a detection rate of 100% for trisomies 21 (n = 43; 95% CI, 87.98–100%), 18 (n = 10; 95% CI, 58.72–100%) and 13 (n = 5; 95% CI, 35.88–100%) with cut‐offs applied to likelihood ratio (cut‐off > 1 considered high risk for trisomy) and probability risk score incorporating adjustment for maternal age (cut‐off ≥ 1/150 considered high risk for trisomy). The false‐positive rate (FPR) was 0% for trisomies 18 and 13 with both analysis outputs. For trisomy 21, a FPR of 0.3% was observed for the likelihood ratio, but became 0% with adjustment for maternal age.ConclusionThis study indicates that the IONA test is suitable for trisomy screening in a high‐risk screening population. The result‐interpretation feature of the IONA software should facilitate wider implementation, particularly in local laboratories, and should be a useful addition to the current screening methods for trisomies 21, 18 and 13. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.