Clinical evaluation of The IONA® test: a non-invasive prenatal screening test for Trisomy 21, 18 and 13.

OBJECTIVE: To evaluate the clinical accuracy of the IONA® test for aneuploidy screening. METHODS: In this multi-centre, blinded study 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. RESULTS: Of the 442 samples, results from 437 were available for analysis and assessment of clinical accuracy. The IONA® test had a detection rate of 100% for trisomies 21 (43 cases, 95% CI 87.98 to 100%), 18 (10 cases, 95% CI 58.72 to 100%) and 13 (5 cases, 95% CI 35.88 to 100%) with cut-offs applied on a likelihood ratio (Cut off >1 considered high risk of trisomy) and a probability risk score incorporating adjustment for maternal age (Cut off ≥1/150 considered high risk of 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 following adjustment for maternal age became 0%. CONCLUSION: This 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 would facilitate wider implementation, particularly in local laboratories, and would be a useful addition to the current screening methods for trisomies 21, 18 and 13.