(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 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 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.
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.
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.
How were those values calculated?
As required by the medical device regulation and for our quality system, we monitor the IONA® test performance in the field. Based on our post-market surveillance, we calculated the IONA® test performance based on reported discordances.
To evaluate accuracy, follow-up diagnostic such as amniocentesis or CVS for abnormal samples and live birth examination for normal samples were requested from laboratories and their referring centres.
It contains data from over 32,000 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.
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.
What shall I do if my IONA® test is high-risk?
The DNA analysed by the IONA® test is of placenta origin (not from the fetus). In rare case, the placenta DNA do not match the fetus DNA. 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 confirmed by a diagnostic procedure. Your healthcare professional will be able to guide you further.
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.