(figures based on testing done by our laboratories on a high-risk population, please note if you are not high-risk, you are likely to have a lower PPV)
The Detection Rate (sensitivity) of IONA® is 99.99%, 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.
The Positive Predictive Value (PPV) is the probability that a high-risk result indicates the presence of the syndrome in question. The PPV takes into account how common that particular syndrome is in the population.
Please click here for further information about the clinical performance of the IONA® Nx test.
What does a high PPV mean for my pregnancy?
A high PPV indicates that the risk of a false positive (non-affected pregnancy falsely screened as high risk, see below) result is minimised.
PPV data for IONA®* is not currently available as the product has not been in the market long enough to receive post-market surveillance data. However, the PPV for the previous version of IONA® was 98.88% meaning that the risk of a false positive (non-affected pregnancy falsely screened as high risk, see below) result was minimal. This meant that if an IONA® test result was high risk for Down’s syndrome, there was only a 1.12% probability that the result is actually a false positive. We are confident the PPV for IONA®* will be at least as high as this and data will be published as soon as it is available.
How are these values calculated?
As required by the medical device regulation and for our quality system, we monitor the IONA® test performance in the field. When adequate post market surveillance data is available, Yourgene will calculate and publish the IONA® test performance based on reported discordances.
To evaluate accuracy, follow-up diagnostic results, such as amniocentesis or CVS and live birth examinations are requested from laboratories and their referring centres.
Who is a high risk population?
Anyone can have a baby with Down's syndrome but a woman's risk increases as she becomes older. If you have previously had a baby with Down's syndrome, your risk of having another affected baby is increased.
Is the PPV always the same?
PPVs are specific to the population and vary based on the NIPT assay.
The PPV of a screening test depends on:
• the prevalence of having a trisomy 21,18 or 13 at a given age,
• the detection rate of the NIPT assay,
As the prevalence of trisomies 21,18 and 13 increase with increasing maternal age, PPVs are lower in low-risk population. You can calculate your PPV for each condition here using the sensitivity and specificity data provided here.
What do I do if my IONA® test result is high-risk?
The DNA analysed by the IONA® test is of placental origin (not from the fetus). In rare case, the placental DNA does not match the DNA of the fetus. For this reason and other biological factor, the IONA® test is a screening test, not a diagnostic test.
Any high risk IONA® result should be discussed with a healthcare professional in the context of all available clinical findings, including advising for the need for genetic counselling or additional diagnostic testing (e.g., amniocentesis).
What are the test performances for Edwards’ syndrome and Patau’s syndrome?
For test performance on Edwards’ syndrome and Patau’s syndrome, please visit Clinical Laboratory Clinical Performance for the latest information.
*IONA® based on the new IONA® Nx NIPT Workflow.