The IONA® test is a leading prenatal screening test for Down’s syndrome with excellent performance.
The Positive Predictive Value (PPV) is the probability that a high risk result indicates the presence of Down’s syndrome. The PPV takes into account how common Down’s syndrome is in the population. The high IONA® PPV (98.88%) means that the risk of a false positive (non-affected pregnancy falsely screened as high risk, see below) result is minimised. This means that if your IONA® test result is high risk for Down’s syndrome, there is only a 1.22% probability that the result is actually a false positive.
The Detection Rate (sensitivity) of IONA® is 99.84%, which means that nearly every case of Down’s syndrome will be detected with very few false negative results (affected pregnancies falsely screened as low risk).
False Positive Rate (FPR) is the proportion of pregnancies that do not have the syndrome but have screened as high risk. A false positive result means that although NIPT indicates a high risk of trisomy 21, the fetus does not have this condition.
We recommend an invasive diagnostic procedure to confirm any high risk IONA® result. Your healthcare professional will be able to guide you further.
PPVs are specific to the population and vary based on the NIPT assay. Figures are based on Post-Market Performance Evaluation of the IONA® test in over 30,000 singleton and monochorionic twin pregnancies, from a population of women who are predominantly at a higher risk of having a fetus with Down’s syndrome.
Positive predictive values are more relevant than sensitivity and specificity for clinical decision and counselling of patients screened for Down’s, Edwards’ and Patau’s syndromes. Indeed, PPV are the actual values observed in the test population. The PPV of a screening test is dependent on the prevalence of the condition within the test population. The prevalence of trisomies 21,18 and 13 increase with increasing maternal age so to calculate the PPV for a specific age group an online calculator can be used (example: https://www.perinatalquality.org/Vendors/NSGC/NIPT ).
For test performance on Edwards’ syndrome and Patau’s syndrome, please visit https://www.yourgene- health.com/for-clinical-laboratories/clinical-labs-clinical-performance for the latest information.
For test performance on Edwards’ syndrome and Patau’s syndrome, please visit Clinical Laboratory Clinical Performance for the latest information.