NIPT Extended

Panorama™

Optimized for screening for sex chromosome maldistributions, microdeletions and in twin pregnancies

What to expect from NIPT Extended (Panorama™)?

Most NIPTs are based on the counting method. This means that the number of DNA fragments that come from the analyzed chromosome, for example, chromosome 21, are counted and compared to the number of fragments from a reference chromosome. This method cannot distinguish between DNA fragments originating from the mother and those from the fetus (more precisely: the placenta).

Natera’s Panorama test is the only NIPT that can distinguish between maternal and fetal (placental) DNA. Therefore, it is particularly suitable for certain questions.

The Panorama test is the only NIPT that can detect triploidies. In a triploidy, one additional chromosome is present from each of the chromosomes. The Panorama test is also optimized for the analysis of sex chromosomes, in particular the question of whether the child will be a boy or a girl, it provides important additional information in twin pregnancies and the results of the recently published SMART study show that the Panorama test has substantial advantages in testing for the 22q11.2 microdeletion (22q, DiGeorge syndrome).

 

The NIPT Extended in twin pregnancies

With its unique SNP technology, the Panorama test is the only NIPT that can determine whether the twins are monozygotic or dizygotic. In most cases, this confirms the result obtained by ultrasound.

Most NIPTs use one of several methods to determine how much maternal DNA and how much fetal (placental) DNA is present in the mother’s blood, the resulting ratio is called “fetal fraction”. This ratio is used to determine whether there is enough DNA information to distinguish between normal chromosome number and trisomy. In the Panorama test, this measurement is made with the help of SNPs. This allows for a rather reliable calculation of the fetal fraction. In twins, other NIPTs determine a combined fetal fraction for both twins together. However, in some cases, the two siblings may have very significantly differing fetal fractions, which can lead to incorrect results when analyzing for trisomy. Only the Panorama test is able to determine a separate fetal fraction for each of the two fetuses.

Likewise, of all the NIPTs, only the Panorama test can determine the sex for both twins separately. The other NIPTs can only tell if both twins are female or if at least one of the twins is male, which in the case of fraternal twins leaves open the possibility that there are two boys or one boy and one girl.

NIPT Extended and testing for sex chromosomes

The determination of fetal sex as a probability of error of about 0.5% for most NIPTs. This means that approx. in one out of 200 cases the fetal sex determination is wrong. Here, too, the Panorama test is an exception. Sex determination with the Panorama test is about 1,000 times more accurate, as shown in a study in which over 1.3 million sex determinations with the Panorama test were evaluated [Obstet Gynecol 2020 May;135(5):1198-1206].

Some parents chose prenatal testing for Turner syndrome. Affected females have only one X chromosome instead of two. Prenatal testing for Turner syndrome may be disturbed by the fact that women can lose the second X chromosome in some cells as they age. This occurrence can cause conventional NIPTs to falsely detect Turner syndrome in the fetus, even though the fetus actually has two X chromosomes. The number of false-positive test results for Turner syndrome is reduced with the Panorama test because it can differentiate whether a fetal X chromosome is missing or whether an X chromosome has been lost in the mother.

The NIPT Extended and testing for 22q

The most common microdeletion is the 22q11.2 microdeletion, also known as 22q or DiGeorge syndrome. The recently completed prospective and multicenter SMART study [doi.org/10.1016/j.ajog.2022.01.002] with over 20,000 participants shows that this microdeletion is significantly more common than previously thought, with a prevalence of approximately 1 : 1500. The performance of the Panorama test in detecting the 22q microdeletion is outstanding. Using the improved IA algorithm, 83.3% of microdeletions could be detected. Of the cases detected as positive, 52.6% proved to be correctly positive, referred to as positive predictive value or PPV. This represents a tremendous improvement over other NIPTs, whose PPV is in the range of only 5%.

In addition to testing for the 22q, the Panorama test also allows testing for four other rarer microdeletions, namely 1p36 deletion syndrome, Prader-Willi, Angelman and Cri-du-Chat syndrome.

What is the testing procedure?

After collection, the blood sample is couriered to the Eluthia laboratory in Giessen, Germany, and sent from there to the Natera laboratory in San Carlos, California. The result of the test is usually available 14 to 21 days after receipt of the sample and is promptly submitted to the ordering gynecologist. The physician then discusses the result with the pregnant woman.

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