Consider the following statements regarding non-invasive prenatal screening (NIPS) for screening high risk pregnancies for aneuploidies: 1. It is carried out on maternal blood. 2. It is done before 10 weeks gestation. 3. It has a negative predictive value of about 98%. 4. Invasive testing is needed for confirmation of a positive test. Which of the statements given above are correct?
NIPS Screening Analysis
Non-Invasive Prenatal Screening (NIPS) analyzes cell-free fetal DNA (cfDNA) from maternal blood to screen for chromosomal abnormalities like aneuploidies.
Statement Evaluation
- Statement 1: It is carried out on maternal blood. This is correct. NIPS technology relies on detecting and analyzing cfDNA fragments originating from the placenta, which are present in the mother's bloodstream.
- Statement 2: It is done before 10 weeks gestation. This is generally incorrect. While NIPS can be performed early, the recommended gestational age typically starts from 10 weeks onwards for optimal accuracy and reliability.
- Statement 3: It has a negative predictive value of about 98%. This is correct. NIPS demonstrates high sensitivity and specificity for common aneuploidies. A high Negative Predictive Value (NPV), often exceeding 99% for conditions like Trisomy 21, indicates that a negative result is highly reliable in ruling out the condition. A value around 98% is a reasonable approximation in the context of screening high-risk pregnancies.
- Statement 4: Invasive testing is needed for confirmation of a positive test. This is correct. NIPS is a screening test, not a diagnostic one. A positive result signifies an increased risk, and diagnostic confirmation typically requires invasive procedures such as Chorionic Villus Sampling (CVS) or amniocentesis.
Conclusion
Based on the analysis, statements 1, 3, and 4 are correct. Statement 2 is incorrect as NIPS is typically performed from 10 weeks gestation, not before.
Important Questions from Congenital Disorders
- To prevent recurrence, expectant mothers with a previous fetus with neural tube defect should receive folic acid daily at the dose of :
- The risk of Down syndrome is 100% in the offspring, if:
Which of the following are examples of genomic imprinting?
1. Angelman syndrome
2. Williams syndrome
3. Prader-Willi syndrome
4. DiGeorge syndrome
Select the correct answer using the code given below:
- To reduce the risk of neural tube defects in the baby, which of the following are recommended?
- A tall thin adolescent boy is found to have gynaecomastia and small testes. His blood testosterone level is undetectable, and serum FSH and LH levels are elevated. Which one of the following is the likely karyotype pattern?
