NIPT

 

 

 

Q.1: What does the abbreviation NIPT stands for?  Ans:  NON-INVASIVE PRENATAL TESTING FROM  MATERNAL BLOOD:

Q.2: Well, this is a screening tets .What chromosomal   abnormalities can be detected from such screening tets(mind you NIPT is not a confirmatory test) . Such chromosomal abnormalities are   aneuploidy for detection of fetal Trisomy 21[Down syndrome],Trisomy 18 [Edwards syndrome],Trisomy 13 [Patau syndrome],Monosomy X (Turner syndrome).

Q 3: When NIPT was designed ? Recently, in last two decades a tets has evolved a special tets which     analyzes fetal Cell-free DAN (cDNA) from maternal plasma and such foetal DNA can be performed as early as 9 weeks of gestation .

 

Q.4: If NIPT is screen positive ,then ?  Ans: For confirmation the age old traditional screening methods  like  CVS and or amniocentesis for detection of foetal  aneuploidy must continue, in addition to NIPT.

 

Q.5:   Prevalence of foetal aneuploidy?? Such foetal aneuploidies are Trisomy 21(Down’s syndrome) ,  Trisomy 18, and Trisomy 13 (the three most common aneuploidies and together occur in approximately 1 in 450 live births) . Of  these, trisomy 21 is the most common.  

 

Q. 6: What was the previous method of screening(still by far the most accepted procedure of parental screening )  for foetal aneuploidies ? Ans;   Until recently, the primary screening involved was serial detection of maternal serum biochemical markers in the first and second trimesters, in combination with first trimester ultrasound to measure nuchal translucency (NT). Although designed to detect Trisomy 21, this integrated screening approach has also detected Trisomies 13 and 18, and increased NT (as well as cystic hygroma and other indicators) is associated with certain sex chromosome aneuploidies

Q.7: What is the distinct advantage of NIPT i.e. fetal cell-free DNA in maternal blood? :

Ans: The identification of fetal cell-free DNA (cDNA) circulating in maternal plasma  now permits a new method of screening for fetal aneuploidies: non-invasive prenatal testing (NIPT) and detects the abnormalities of  foetus as early as 9 weeks of cession. By having this information the Obstetrician is in better position to counsel for  CVS and can recommend for CVS with confidence for confirmation.

Q,8:  How does foetal DNA come into maternal circulation ?? Because fetal cDNA traverses the blood-placental barrier ad enters maternal circulation, a simple maternal blood draws for detection of fetal chromosomal copy number while avoiding the risks of invasive procedures.

utilization of the dna-mb test

Q.9: What is the method used in NIPT ? Ans . This is called DNA-MB test  which however can be performed as early as nine weeks gestation—earlier than any other test and consists of a simple blood draw. For sample collection, special blood tubes are used which protect the cDNA, and these are sent at room temperature to laboratory. After samples are processed, a report is generated that contains risk scores for each of the chromosomes evaluated.

Q. 10: Is foetal sex chromosome is reported? Ans Usually not, But those fatal syndromes transmitted by X-linked genes in these cases sex chromosome of foetus may be mentioned in the report page .Fetal sex Chromosome anomalies are reported, if requested. (In accordance with local laws in force).

Q. 11. Next what if abnormal chromosome report comes from study of foetal DNA ? Ans: For patients identified as high-risk for fetal chromosomal abnormality, follow up testing & genetic counseling is recommended for patients.

What is microdeletion?? Is it possible to detect microdeletions. ? Microdeletions i.e. a small, missing (or “deleted”) piece of a chromosome is called a microdeletion. DNA MB NIP test also offers the option of testing for microdeletions. These microdeletions result in syndromes that can have severe intellectual disability, and moderate to severe physical disabilities. Microdeletions are usually not inherited from a parent. They are not more common in older mother, as Down syndrome is. In many cases, there are no obvious ultrasound abnormalities that would suggest the fetus has microdeletions. Nothing one ptegnant woman do before or during her  pregnancy can cause a micro deletion. Some microdeletions cause intellectual disability and birth defects, while others have little impact on a child’s health and life. chorionic villus sampling (CVS), these are invasive and carry a risk of miscarriage. The DNA-MB NIP test requires only a blood draw from the mother, and is safe for mother and baby. The unique methodology of the DNA-MB test utilizes single nucleotide polymorphism [SNP] technology. Aneuploidy testing Using SNPs methodology evaluates specific genetic loci on the actual mix of maternal and fetal DNA from the mother’s blood. This allows the DNA-MB prenatal test to provide high sensitivity and specificity across all chromosomes, even at low fetal fractions. The result is an individualized risk score, and better sensitivity and specificity with a decreased chance of false positives or false negatives

 

.Q.12: Prevalence of microdeletions??  The combined incidence of these microdeletions is approximately 1 in 1,000 births. While there are diagnostic tests available, like amniocenteses of chorionic villus sampling (CVS), these are invasive and carry a risk of miscarriage. The DNA-MB NIP test requires only a blood draw from the mother, and is safe for mother and baby.

Q.13:-How does the DNA-MB test work?

During pregnancy, some of the DNA from the baby crosses into mom’s bloodstream. DNA is organized in structures known as chromosomes, which carry the baby’s genetic information.  Such  a laboratory who works on  DNA-MB test  uses a blood sample from the mother that analyzes the baby’s DNA for certain chromosome conditions that could affect the baby’s health. This screening test is a non-invasive prenatal test (NIPT). This means that the DNA-MB test is safe for baby(as noninvasive) .

While fetal fraction of SNA (Single  nucleic acid) in the mother’s blood can vary greatly throughout gestational age, it does tend to be lower earlier in the pregnancy, by using SNP(Single  nucleotide polymorphism)  technology, the DNA-MB prenatal test has high accuracy even at lower fetal fractions and can be used as early as 9 weeks gestational age.

DNA-MB prenatal test, accurate and comprehensive non-invasive screening test.

We know that most people have 23 pairs of chromosomes for a total of 46—tow copies of each set. The DNA-MB NIP test is highly accurate in screening for instances where there is only one chromosome where there should be a pair, of if there is an extra chromosome, specifically for the chromosomes that are responsible for Down syndrome, Edwards syndrome, Patau syndrome and certain sex chromosome trisomies.

DNA-MB NIP test can also identify if there are three sets of each chromosome, which is known as triploidy.

DNA-MB NIP test also offers the option of testing for microdeletion. These microdeletions result in syndromes that can have severe intellectual disability, and moderate to severe physical disabilities. Q. 15: How sensitive is  NIPT to pick up chromosomal abnormality??

Trisomy 21                       99%

[Down syndrome]

Trisomy 18                        99%

[Edwards Syndrome]

Trisomy 13                         92%

[Patau Syndrome]

Monosomy X                      94%

[Turner Syndrome]

Sex Chromosome               99%

[Trisomies]

 

 

At Kolkata: It is the practice of most Labs who are doing such maternal blood tests is as follows . Maternal blood is drawn at home & blood is sent to Lab for “Double-Verifications” i.e. one test they do themselves at Kolkata & routine cross checking is carried out from abroad.

That was the practice 3 yrs back, Charges: [a] 18,000|-for blood test alone.                  [b] 9,000|--for  CVS  if warranted . Amniocentesis 13,000/-... Report -7 to 8 days [Maximum]... Accuracy – 98% with CVS  , Amniocentesis it will become 100%. Time        -After 9 wks from date of last period.

 How does DNA test compare to an Ultrasound, CVS and Amniocentesis?

Method                      Invasive                 Performed at:                     Timing                    Accuracy

DNA                                NO                          Home                              9Weeks [+]                  98%

CVS                                  Yes                          Clinic                                9 Weeks [+]               98%

Amniocentesis               Yes                           Clinic                                14 Weeks [+]               98%

Ultrasound                      No                            Clinic                                 14 Weeks [+]              80%

Take home message: DNA-MB test offers superior overall performance when detecting Trisomy 21, Trisomy 18, Trisomy 13, Monosomy X, and fetal sex chromosome abnormalities. The low false-positive rate will reduce the number of unnecessary invasive diagnostic procedures when compared to biochemical and ultrasound screening methods, and offers early reassurance.

Professional organizations such as the American college of obstetricians and gynecologists and the International society of Prenatal Diagnosis have already recommended cDNA-based testing for non-invasively screening for fetal aneuploidies ONLY IN HIGH RISK pregnant  women.,