Results interpretation and procedures to follow:

• For autosomal aneuploidies (other than trisomy 21, 18 and 13 and imbalances greater than 7 MB):

In these cases, the false positive rate is higher than in traditionally screened aneuploidies (21, 18, 13).

Mosaicism can be seen with any chromosomal anomaly. Its prevalence in rare trisomies and in partial chromosome imbalances is higher than in the trisomies of chromosomes 21, 18, and 13. Confined placental mosaicism can occur, leading to a false positive result. In these conditions, the prognosis is variable, and depends on the individual case.
As the NIPT is a screening test, results should be considered within the context of the overall pregnancy picture and positive results should be confirmed (for example, by CVS or amniocentesis) prior to making irreversible pregnancy management decisions. A case-by-case discussion should be conducted by health professionals.

• For sex chromosome aneuploidies:

There is an increased possibility of false positive results for sex chromosome aneuploidies as part of the screening test.
Once a positive result is confirmed, it may have a variable prognosis (e.g., Turner syndrome). A case-by-case discussion should be conducted by health professionals prior to making irreversible pregnancy management decisions. Patients should be referred to genetic counsellors to receive accurate, balanced, up-to-date information when an increased risk of sex chromosome aneuploidy is reported after NIPT.

Eurofins Biomnis geneticists are available for any question related to result interpretation at International@biomnis.eurofinseu.com.