CARRIER SCREENING TEST, latest information

A carrier screening test, also known as genetic carrier screening, is a blood test that determines if a person carries a gene mutation that could increase the risk of passing on a genetic disorder to their child. The test can be performed before or during pregnancy.

1. CARRIER SCREENING TEST
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2. CONTENT
➢Introduction
➢Types of carrier screening tests
➢Role of carrier screening test in India
➢Genetic disorders in India
➢Reasons for carrier screening test
➢Test process
➢Result Interpretation
➢Implications
➢Ethical consideration
➢Conclusion

3. INTRODUCTION
➢Determines if someone has a genetic variation that could increase the risk of
their child being affected by a genetic condition.
➢The test usually involves a blood sample from one or both parents.
➢Carrier screening is optional and is often considered when someone is
planning pregnancy.
➢Carrier screening looks for variant alleles in genes associated with a disease.
➢A carrier has inherited a normal and a variant allele for a disease-or trait-
associated gene, one from each parent.
➢Everyone carries abnormal genes, and in general, carriers have no symptoms
or signs of the disease they carry.

4. Types of Carrier Screening Tests
Basic Carrier Screening
➢It is a targeted screening.
➢Focuses on specific genetic
mutations known to cause
particular disorders.
➢Screens for cystic fibrosis (CF),
spinal muscular atrophy (SMA),
and conditions that occur more
often in people of certain ethnic
groups.
Expanded Carrier Screening
➢Screens for multiple genetic
conditions simultaneously,
offering broader insights.
➢Screens for more than 100 genetic
conditions, including CF and
SMA.
➢Sometimes, no carrier screening.

5. Why is the screening test critical in India?
Over 56M
people with
single gene
disorder.
More than
50L babies
born with
genetic
disorders each
year.
20%-30% of
all infant
deaths are
due to genetic
disorders.
1 in 100
babies born
with an
inherited
disease.

6. Most Common Genetic Disorders in India
Autosomal Recessive Disorders
➢Beta Thalassemia
➢Sickle Cell Anaemia
➢Cystic Fibrosis
➢Congenital Adrenal Hyperplasia
➢Spinal Muscular Atrophy
X-linked Recessive Disorders
➢Duchenne Muscular Dystrophy
➢Haemophilia A/B
➢Hunter Syndrome
➢G6PD Deficiency
➢X-linked Mental Retardation

8. Why screen for inherited genetic conditions?
➢Each individual harbors an average of 2.8 known severe
recessive mutations.
➢Carriers are usually healthy or unaffected but risk passing
their genetic condition to their children. Traditionally, carrier
screening has been offered to patients based on their ethnic
background or family history.
➢However, more than 80% of babies born with inherited genetic
diseases have no known family history.

9. When should a couple get tested?
A couple can get tested in the following situations:
➢Preconception-when the couple is planning for a baby.
➢Prenatal Diagnosis (early pregnancy)-with a history of the previous
child affected for getting to know the status of the present
pregnancy.
➢Before an IVF procedure.
➢Before a Preimplantation Genetic Diagnosis (embryo selection).
➢Before the use of a donor sperm and/or oocyte.

10. Who should get tested?
Carrier testing helps determine one's carrier status and is an essential
step of the family planning process.
However, the test is strongly recommended in the following cases:
➢Consanguineous marriage.
➢Either partner is affected by a hereditary disorder.
➢History of a genetic disorder in the family.
➢History of multiple pregnancy losses.
➢Couple from an ethnic group with a high carrier rate of certain
genetic disorders.
➢Congenital anomalies detected in children.

11. How do we test for these disorders?
➢Most tests are based on Next-Generation Sequencing (NGS) and
Multiplex Ligation Probe Amplification (MLPA) technologies.
➢Enables the detection of disease-causing mutations in over 2000
genes (Autosomal Recessive and X-linked recessive).
➢NGSis a best-in-class and superior technology to detect all common
and rare disease-causing mutations, while MLPA is used to detect
deletion and duplication in specific genes (e.g., SMN, DMD,
CYP21A2).

12. NGS VS GENOTYPING
Next Generation Sequencing
➢Used by a few providers to
comprehensively evaluate the gene.
➢Test for 5-10 times more pathogenic
mutations and detect all common and
rare disease-causing mutations.
➢Delivers high accuracy across
ethnicities.
➢Enablsthe discovery of rare and novel
mutations in a pan-ethnic population.
➢Low residual risk, regardless of
ethnicity.
Genotyping
➢Used by many companies for
routine carrier screening.
➢Tests for a limited set of common
mutations.
➢Provides limited utility beyond
Caucasian and Jewish ethnicities
➢Fails
➢Fails

13. The Test Process
1. TRF 2. Sample 3. Testing
4. Reporting 5. Counselling

14. Interpretation of Results
➢Negative Result:
Indicates no known mutations detected.
➢Positive Result:
Indicates the presence of one or more mutations.
Further counseling and testing may be recommended.

15. Genetic Counselling
➢Provides clear, concise information about genetic conditions.
➢Evaluate individual and familial risk factors.
➢Guides informed decision-making regarding testing and interventions.
➢Offers counseling for coping with emotional and psychological impacts.
➢Ensures confidentiality of genetic information.
➢Offers ongoing support and follow-up for evolving needs.
➢Acts as a patient advocate in navigating healthcare systems.
➢Empower individuals to take control of their genetic health.
➢Provides access to additional support services and resources.

16. Implications of Carrier Screening
Family Planning:
Allows informed
decision-making
regarding
reproductive choices.
Prenatal Testing:
Enables early
detection and
management
options for
affected
pregnancies.
Emotional
Impact:Can
evoke anxiety,
uncertainty, or
relief based on
results.

17. Ethical Considerations
➢Autonomy: Respect for individuals' choices regarding testing and
reproductive decisions.
➢Informed Consent: Ensuring individuals understand the purpose,
risks, and implications of testing.
➢Privacy: Safeguarding genetic information and maintaining
confidentiality.
➢Equity: Addressing disparities in access to testing and counseling
services.

18. CONCLUSION
➢Carrier screening tests play a crucial role in reproductive
healthcare by identifying individuals at risk of passing on
genetic disorders.
➢Understanding the implications and ethical considerations
surrounding carrier screening is essential for informed decision-
making.
➢Encouraging open dialogue and access to comprehensive
counseling services is vital for supporting individuals through
testing.

19. THANK YOU
REFERENCES :
https://www.acog.org/clinical/clinical-guidance/committee-
opinion/articles/2017/03/carrier-screening-for-genetic-conditions
https://diagnostics.medgenome.com/carrier-screening-test/
https://www.pennmedicine.org/for-patients-and-visitors/find-a-
program-or-service/obstetrics/prenatal-genetic-testing/diagnosis-and-
screening-services/carrier-screening