Carrier Screening: What it is & Why it Matters?

Introduction

Did you know 1 in 4 couples carries a genetic condition that could affect their children? This often occurs unknowingly, and most couples only find out after pregnancy. This makes carrier screening, a type of preventive screening test, very important. Carrier screening helps uncover genetic risk factors, empowering couples to make informed decisions about family planning.

Let’s delve deeper into what carrier screening is and why it matters!

What is Carrier Screening?

Carrier screening is actually a genetic test that identifies whether one or both partners carry genes associated with inherited genetic disorders. A ‘carrier’ is an individual who has one copy of the gene mutation (abnormal changes in the genes) that can cause a disease or condition if it is passed to their child. A carrier typically shows no symptoms.

Here’s an interesting fact: Genetic conditions follow predictable inheritance patterns.

• If both parents are carriers of the same recessive condition, there is a 25% chance in every pregnancy that their child will have the condition.
• If only one parent is a carrier, the child cannot develop the disease, but may become a carrier.
• Some diseases follow X-linked inheritance, meaning the risk can differ depending on whether the mother or father carries the gene. 

It is essential to distinguish genetic carrier screening for couples (healthy individuals) from diagnostic testing, which evaluates symptoms of a known or suspected disease. Carrier screening is performed on the parents to check for genetic variations. It is usually performed before a pregnancy. Diagnostic screening, on the other hand, is performed on the individual with the disease or condition.

Why Carrier Screening Matters for Families

Carrier screening empowers couples to make informed choices and helps families plan for their future. It also supports:

• Reproductive decision-making: Understanding potential genetic risks enables timely medical and personal planning.
• Informed IVF or fertility choices: Couples using assisted reproductive methods like IVF can opt for genetic safety assurance through embryo testing before implantation.
• Early awareness: Premarital genetic testing enables couples with known family histories or consanguineous marriages to take preventive measures.

Common Genetic Conditions Detected by Carrier Screening

Carrier screening helps detect several inherited genetic conditions, such as:

Blood Disorders

• Thalassemia (Alpha and Beta) carrier screening
• Sickle anaemia: Affects the formation of haemoglobin, leading to anaemia and pain crises.

Metabolic Disorders

• Cystic fibrosis: Affects lung and digestive function
• Phenylketonuria: Impairs protein metabolism
• Gaucher Disease: Causes organ enlargement and bone problems.

Neuromuscular Conditions

• Spinal Muscular Atrophy: Progressive muscle weakness in infants and children.
• Duchenne Muscular Dystrophy: An X-linked disorder causing muscle degeneration.

Other Conditions

• Fragile X Syndrome 
• Haemophilia

Who Should Consider Carrier Screening?

Any couple planning to have children can benefit from carrier screening. However, some groups who have a higher need for carrier screening are:

• Couples planning pregnancy or IVF
• Individuals with a family history of genetic disorders 
• People of specific ethnic backgrounds –
  • Mediterranean: Thalassemia, Familial Mediterranean Fever
  • Ashkenazi Jews: Tay-Sachs, Gaucher Disease
  • African: Sickle Cell Disease
  • South/Southeast Asian: Thalassemia, G6PD deficiency

Undergoing genetic carrier testing is actually encouraged in some regions of the world, especially in communities known for consanguineous marriages.

In addition to these groups, carrier screening is recommended even for carriers with no family history.

The Carrier Screening Process

If you wish to undergo a carrier screening test with us at FSG Labs, here’s what the process looks like:

1. Sample collection
   The first step in the carrier screening process is the collection of a blood sample or taking a cheek swab. Sample collection is quick, non-invasive and can be done before or early in pregnancy. 

2. Laboratory analysis
   The collected sample is sent to a laboratory. At FSG, we use modern NGS (Next Generation Sequencing) technology that reads thousands of genes at once, while PCR and Sanger Sequencing confirm specific mutations. 

3. Results
   The results of a carrier screening test usually take 2 to 4 weeks to arrive. 

4. Result interpretation
   The report will typically contain ‘negative’ or ‘positive’ for the diseases tested. Once you receive the report, visit your healthcare provider for further steps.

Understanding Your Carrier Screening Results

A carrier screening test result will show one of two results for different diseases or genes:

• Negative: No carrier status detected for tested conditions (though not all diseases can be screened).
• Positive: Carrier of one or more conditions. In this case, a partner should undergo testing and genetic counselling is advised.

It is important to note that a negative result reduces but does not eliminate genetic risks, since not all genes are known or testable. At the same time, positive results do not mean you are sick. Most carriers are completely healthy. 

The primary reason for testing is to help in reproductive planning, especially when both partners carry the same recessive gene. 

If both partners are carriers, genetic counsellors usually discuss the following probabilities per pregnancy:

• 25% chance the child will have the condition
• 50% chance the child will be a carrier
• 25% chance the child will be unaffected

Reproductive Options When Both Partners Are Carriers

If both partners happen to be carriers of the same condition, they can still go ahead with family planning. At First Stem Cell and Genomics Lab, our board-certified counsellors offer personalised guidance and support at every stage to eliminate any genetic conditions in children.

These include:

• Preimplantation Genetic Testing (PGT) during IVF to identify unaffected embryos.
• Prenatal testing, such as Non-Invasive Prenatal Testing (NIPT) or diagnostic testing during pregnancy, is used for early detection.
• Use of donor gametes (sperm or egg) to prevent passing down carrier genes.
• Adoption is an option for families choosing alternative parenthood paths.

Genetic counselling ensures families understand their risks and make informed decisions based on the implications of the different options available to them.

Carrier Screening vs Other Genetic Tests

Carrier screening is also a genetic test, but it differs significantly from others. Here’s a brief comparison of various genetic tests available at FSG Lab, Dubai:

Common Misconceptions About Carrier Screening

While genetic testing has been used for a few decades, carrier screening is relatively new, and most people lack adequate knowledge about it. This results in myths and misconceptions around the test. Here are a few common misconceptions and their facts!

• Myth 1: Only people with a family history should undergo carrier testing
  Truth: About 80% of babies with genetic diseases are born to parents with no family history. 
• Myth 2: Being a carrier means having the disease
  Truth: Carriers are healthy but can pass on the affected gene. 
• Myth 3: If I’m a carrier, my child will definitely have it
  Truth: Even if both parents carry the same gene mutation, the chance is just 25%. 
• Myth 4: Carrier screening is for women only
  Truth: Both men and women can undergo screening. 
• Myth 5: The test is complicated or invasive
  Truth: It is a simple blood test with results available in 2 to 4 weeks. 
• Myth 6: It is pointless during pregnancy
  Truth: Carrier screening can still guide prenatal testing and care decisions.

The Role of Genetic Counselling

You have undergone carrier screening. What’s next?

If your test results indicate a risk for certain genetic conditions, it is essential to meet certified genetic counsellors, who play a vital role in supporting couples through the carrier screening process. 

A genetic counsellor helps interpret results, explain genetic risks, and discuss reproductive and emotional considerations. You can seek genetic counselling:

• Before carrier testing, to understand its purpose 
• When both partners are carriers
• When making decisions about IVF, PGT, or other reproductive strategies

Your genetic counsellor will perform a complete family health review, personal risk assessment for each partner based on test results, and discuss the various reproductive options available to the couple. 

Integration with Other Reproductive Health Testing

Carrier screening can be combined with several reproductive health testing panels. Some of the tests that are routinely recommended along with carrier testing include:

1. As part of preconception care (Preconception carrier screening)
2. Combined with fertility testing
3. Integration with IVF planning
4. Chromosomal analysis in the case of recurrent miscarriages
5. Y-chromosome deletions in men
6. Chromosomal imbalance in women
7. Preimplantation genetic testing for identified carrier conditions
8. Ensuring a healthy embryo transfer

Advances in Carrier Screening Technology

Thanks to advanced genetic techniques like Next Generation Sequencing (NGS), the scope of carrier screening has expanded, now covering over 300 conditions with higher accuracy and lower cost. It marks a significant shift from single-gene tests to comprehensive genetic profiling.

In the near future, genome-wide screening and integration with precision medicine will allow more personalised risk assessments, ensuring better reproductive outcomes. Always ensure you opt for an accredited, GMP-certified laboratory to process your test for the highest quality standards.

Making the Decision: Is Carrier Screening Right for You?

You can undergo carrier screening to help you determine your family planning goals and assess or detect any genetic conditions running in your family, especially if you belong to an ethnic background with a high risk for certain conditions.

Benefits

Carrier screening offers several benefits to those undergoing the test:

• Gives you peace of mind when results are negative
• Empowers couples, enabling them to make informed decisions
• Gives an early time frame for medical or emotional preparation

Limitations

Despite the advances, carrier screening still has a few limitations:

• Does not screen for all genetic conditions 
• There is still some residual risk even after negative results
• Requires one to visit a genetic counsellor for an accurate interpretation of test results

Conclusion: Empowering Family Planning Through Knowledge

Knowledge about a disease or condition empowers one to make informed, logic-driven decisions. This is exactly what carrier screening does– it bridges the gap between genetics and proactive, preventive healthcare. It offers couples clarity, time and confidence to plan their families and navigate the genetic risks their children are susceptible to.

Planning a family now or in the near future? Talk to your healthcare provider about carrier screening. Schedule a consultation with our genetic counsellors and take the first step towards empowered parenthood.