Carrier Screening

Targeted carrier screening testing focuses on detecting common variants associated with specific genetic conditions, typically based on ethnic background or family history. On the other hand, expanded carrier screening test assesses a broader range of genetic disorders, covering both common and rare conditions across all ethnicities.

Recessive genetic disorders happen when an individual inherits two copies of a defective gene, one from each parent. These disorders are usually not present in carriers, who are typically healthy but can pass the defective gene to their children.

When both parents are genetic carriers, there is a chance of having an affected child, a 50% chance of having a child who is also a carrier, and a 25% chance of having a child who is neither affected nor a carrier. Some common examples of autosomal recessive disorders include Cystic Fibrosis, Beta Thalassemia, and Spinal Muscular Atrophy.

• Purpose: Carrier Screening identifies inherited genetic variants in parents, while NIPT detects chromosomal abnormalities in the fetus.
• Timing: Carrier Screening is done pre-conception or early in pregnancy; NIPT is done during pregnancy (typically after 10 weeks).
• Focus: Carrier Screening targets autosomal recessive or X-linked disorders (e.g., SMA, Cystic Fibrosis); NIPT screens for fetal trisomies (e.g., Trisomy 21).
• Who is tested: Carrier Screening analyses parental DNA; NIPT analyses fetal DNA through a maternal blood sample.
• Outcome: Carrier Screening assesses reproductive risk; NIPT evaluates the likelihood of fetal chromosomal abnormalities.

Carrier Testing can diagnose a wide range of autosomal recessive and X-linked recessive disorders. Some of the most common conditions include:

• Beta Thalassemia
• Sickle Cell Anemia
• Cystic Fibrosis
• Spinal Muscular Atrophy (SMA)
• Duchenne Muscular Dystrophy
• Hemophilia A/B
• Congenital Adrenal Hyperplasia (CAH)

The Carrier Screening Panel analyses an individual’s DNA to detect variants in genes linked to autosomal recessive and X-linked recessive disorders. It uses two technologies:

1. Next Generation Sequencing (NGS): Detects all common and rare gene variants.
2. MLPA (Multiplex Ligation Probe Amplification): Identifies deletions and duplications in specific genes, such as SMN (for Spinal Muscular Atrophy) and DMD (for Duchenne Muscular Dystrophy).

• Test Ordered: Physician recommends carrier screening based on medical history or during preconception planning.
• Sample Collection: A simple blood sample is collected from each partner.
• Testing Process: DNA is analysed using NGS and MLPA to detect variants in 2,000+ genes.
• Turnaround Time: Results are ready in 21 days (Silver/Gold panels) or 28 days (Platinum panel).
• Reporting & Counselling: Results are shared with the physician, and genetic counselling is offered to the couple.

The Carrier Screening Test is recommended for:

• Individuals with a family history of genetic disorders or those with multiple pregnancy losses.
• Couples in consanguineous marriages (related by blood), as the risk of passing on genetic disorders is higher.
• Anyone from an ethnic group with a high carrier rate for certain genetic disorders.
• Couples planning a pregnancy or those undergoing IVF or Preimplantation Genetic Diagnosis (PGD).

The results of a Carrier Screening Test can be classified into three categories:

• Carrier: If an individual is a genetic carrier, they have one copy of a mutated gene but do not show symptoms. If both partners are carriers of the same condition, they should consult a genetic counsellor to discuss the risk of passing the disorder to their children.
• Non-Carrier: A non-carrier result indicates no disease-causing variants were found in the genes tested, significantly lowering the risk of passing genetic disorders.
• Inconclusive: Occasionally, results may be inconclusive, and further testing might be required to get a clearer picture.

• Largest CAP-accredited genomics lab in South Asia: Ensures high standards of accuracy and quality.
• Comprehensive coverage: Screens for over 2,000 genes, identifying both common and rare genetic disorders across all ethnicities.
• Best-in-class technology: It utilises Next-Generation Sequencing (NGS) and MLPA, providing high accuracy and low residual risk regardless of ethnicity.
• Expert genetic counselling: Premarital carrier screening and consultations with certified, multilingual genetic counsellors to help interpret results.
• Pan-India presence: Convenient sample collection across India, with a fast turnaround time of 14-28 days.