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Introduction

Throughout the early stages of human development, the vast majority of fetal chromosome abnormalities result in miscarriage. However, there are a small, but significant proportion of chromosome abnormalities that persist and if undetected, can manifest ass chromosome disease syndrome after birth. these chromosome abnormalities include DownSyndrome(trisomy 21), Edward Syndrome (trisomy 18) and Patau Syndrome(trisomy 13) as well as a range of sex chromosome abnormalities (SCAs) such as Turner Syndrome(45,XO), Klinefelter Syndrome(47,XXY),Triple X Syndrome(47,XXX) and JacobSyndrome (47,XYY). In addition to these 7 chromosome diseases, the fetus may also lose a small part of a chromosome and result in microdeletion syndrome. Although rare, the 7 most frequent microdeletion syndrome include 22q11.2(DiGeorge), 1p36, 2q33.1, 5p(Cri-Du-Chat),8q23-24(Langer-Giedion), and 15q11-13(Angleman/Prada-Willi).

How does the Foresight test detect fetal chromosome syndromes?

During pregnancy, fetal DNA derived from placental cells is released into the maternal blood where it mixes with maternal plasma DNA. On average, the fetal DNA fraction ath the end of the first trimester is around 10% and increases approximately 1% per gestational week. Recent research has shown that the fetally derived DNA fragments are slightly smaller in size than the maternally derived DNA fragments, thus enabling fetal DNA to be distinguished from maternal DNA based on size parameters.

The Foresight test is an advanced technology that uses paired end sequencing of unamplified maternal and fetal plasma DNA to directly generate millions of sequencing reads and count the proportion of DNA fragments for each of the 24 fetal chromosomes. By comparing the fetal DNA counts from the test sample to the fetal DNA counts of a control reference sample,on a chromosome-by-chromosome basis, unexpected changes in normal counts indicate the presence of a fetal chromosome abnormality.

For example, if the fetal DNA counts for chromosome 21 are found to be 1.5 fold higher, this indicates a change from two normal copies to three abnormal copies(trisomy), thus indicating to a high fetal risk for Down Syndrome.

Chromosome Disease Newborn Incidence Clinical Disease Phenotype
Down syndrome (trisomy 21) 1/700 Characteristic facial features, multiple malformations, growth retardation, mental retardation, reduced lifespan
Edward syndrome(trisomy 18) 1/3500-1/8000 Congenital heart disease, multiple organ abnormalities, growth retardation. Most features die in utero, 40% die within the first month, 5% live past their first year and only 1% live beyond 10 years
Patau syndrome 1/25000 Most fetuses (>95%)die in utero. More than half the newborns have severe facial abnormalities combined with congenital heart disease and die within six months
Turner syndrome(45,X) 1/2500(female) Short stature,abnormal sexual development,lower level of intelligence
Klinefelter syndrome(47,XXY) 1/500-1/1000(male) Elevated height,smaller bilateral testes,breast enlargement,infertility or sexual dysfunction,lower level of intelligence
Jacob syndrome(47,XYY) 1/1000(male) Subfertility,learning disabilities and delayed development of speech,language skills and motor skills(sitting and walking),weak muscle tone, hand tremors and some involuntary movements
Triple X syndrome(47,XXX) 1/1000(female) Slightly altered body appearence. Exhibit learning disabilities and delayed development of speech and language skills. Delayed development of motor skills(such as sitting and walking) and weak muscle tone
22q11.2 deletion syndrome(DiGeorge) 1/4000 Distinctive facial features, heart and kidney abnormalities, immune system disorders, developmental delay in language, learning abilities, and attention deficit hyperacivity disorder
1p36 deletion syndrome 1/5000-1/10000 Distinctive facial features,vision or hearing problems,heart abnormalities, epilepsy, weak muscle tone, multiple malformations, severe speech problems, and temper tantrums
2q33.1deletion syndrome Rare Characteristic facial features, epilepsy, growth retardation,severe speech problems,feeling difficulties,behavioral problems,including hyperactivity and aggression, repeat movements
Cri-Du-Chat syndrome 1/20000-1/50000 Infants have high-pitched cry that sounds like a cat. Distinctive facial features, weak muscle tone,growth retardation, behavioural problems, including hyperactivity and aggression,repeat movements.
langer-Giedion syndrome(8q23-24deletion Rare Sparse scalp hair,loose skin, multilpe benign bone tumors, and small brain
Angelman syndrome(15q11-13 maternal deletion) 1/12000-1/20000 Face appearence as "happy puppet". Development delay, intellectual disability, delayed speech, inability to walk, move or balance.
Prader-Willi syndrome(15q11-13paternal deletion) 1/10000-1/30000 Weak muscle tone,underdeveloped genitalia, obesity,small hands and feet and short stature

Why choose the Foresight Early NIPS Plus test?

Based on clinical performance indicators of over 20,000 pregnancies tested, the new Foresight test exhibits unprecedented reliability and accuracy for detecting fetal chromosome abnormalities:

  • High sensitivity
    • -99.62% for trisomy 21, 99.67% for trisomy 18 and 100% for trisomy 13
    • -100% for combined SCAs 45XO,47XXY, 47XXX and 47XYY
  • Very low false-positive rates
    • -0.03% for trisomy 21, 0.02% for trisomy 13
    • -0.14% for combined SCAs 45XO, 47XXY, 47XXX and 47XYY
  • Additionally detects 7 microdeletion syndromes
  • Measures the fetal DNA fraction percentage
    • -an internal quality control indicator to ensure the validity and accuracy of the test result

Clinical indications for the Foresight test

The test is available to all women with an established pregnancy conceived either naturally or by assissted conception, according to the following clinical criteria.

  • Singleton pregnancy (gestational age>10 weeks)
  • Twin pregnancy(gestational age>12 weeks
  • High risk of fetal chromosomal abnormality by maternal serum screening/abnormal ultrasound scan
  • Paternal or maternal carrier of a Robertsonian translocation

Contradictions for Foresight test

For some maternal situations, it will not be possible to offer NIPS testing due to confounding factors that alter the normal maternal plasma DNA profile:

  • A cancer diagnosis
  • Stem cell transplantation therap y
  • Blood transfusion

Patient blood collection procedure

All patients will be provided with a Foresignt Early NIPS blood collection kit containing a Streck tube, patient information sheet and consent form. Your doctor will discuss the content of the patient information sheet and you must sign the consent before undertaking the test. Following consent, your doctor or nurse will collect 10ml of venous blood into the streck tube and send to the testing laboratory.After receipt of your blood sample(usually within 2 days),the turnaround time for performing the test and issuing a report to your doctor is 5-7 business days.

Your doctor will be emailed a detailed report witha visual graphic chromosome display that summarizes the fetal risk of a trisomy or SCA. A low risk indicates that a fetal chromosome abnormality was not detected(negative result). A moderate or high risk indicates that a fetal chromosome abnormality was detected(positive result). In the case of a positive result,your doctor may recommend further medical intervention such as invasive amniocentesis and karyotyping to confirm the NIPS test result.

Additional test information

  • The test is a screening test, not a diagnostic test. Thus, while the test is highly accurate, it does not guarantee 100% accuracy.
  • The test does NOT report the sex of the fetus
  • Due to the influence of biological and genetic factors such as vanishing twin, confined placental chromosome mosaicism, an altered maternal karyotype or an unidentified maternal tumor, around 5-10% of all positive results will be false positive whereby the fetus will not be inflicted with a chromosome disease syndrome.
  • In pregnancies where the measured fetal DNA fraction is less than 4%, a test report will not be issued due to compromised accuracy. In these cases, we recommend re-testing at 2-3week more advanced gestational age when fetal DNA fraction generally increases

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