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(Please note this information has been generated from the testing performed specifically by our laboratory. If your pregnancy is not considered as high-risk, you are likely to have a lower PPV)

The Detection Rate (sensitivity) of IONA® is 99.99% for Down's syndrome. This means that nearly every case of true trisome 21 will be detected by the test with very few false negative results (affected pregnancies falsely screened as low risk). The sensitivity for trisomy 18 and 13 is similar to that of trisomy 21.

False Positive Rate (FPR) is the proportion of pregnancies that do not have the syndrome but return a high risk screening result. A false positive result means that although NIPT indicates a high risk of trisomy 21 (or 13, or 18), the fetus does not in fact have this condition.

Positive Predictive Value (PPV) is the probability that a high-risk result indicates the presence of the syndrome in question. Unlike Detection Rate (sensitivity), PPV takes into account how common that particular syndrome is in the population.

IONA test trisomy 21 performance data according to maternal age

Please click here for further information for healthcare professionals 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.

What is the PPV for the IONA® test?

The PPV for Down's syndrome for IONA®* is 99.50% meaning that the risk of a false positive (non-affected pregnancy falsely screened as high risk) result is minimal. This means that if an IONA® test result is high risk for Down’s syndrome, there is only a 0.50% probability that the result is actually a false positive.

For test performance for Edwards' syndrome and Patau's syndrome, please visit Clinical Laboratory - Clinical Performance for the latest information.

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. Observed performances are based on Post-Market Surveillance of the IONA® Nx test in over 9,575 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.

To evaluate accuracy, follow-up diagnostic results, such as amniocentesis or CVS and live birth examinations are requested from laboratories and their referring centres.

What do you mean by 'high-risk population'?

Down's syndrome does not run in families in almost all cases. A woman’s chance of having a baby with Down's syndrome increases as she gets older, but anyone can have a baby with Down's syndrome. 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 used.

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 factors, 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 findingsand should include advice regarding the need for genetic counselling or additional diagnostic testing (e.g., amniocentesis).

*IONA® based on the new IONA® Nx NIPT Workflow.