Genetic Testing: What You Need to Know

What is genetic testing?

Genetic testing, sometimes referred to as genomic testing, is a medical procedure that examines your DNA to identify changes in your genes, chromosomes, or proteins. These changes, known as mutations or variants, can be linked to a range of health conditions, some of which may be inherited or increase your risk for certain diseases.

What is the purpose of genetic testing?

There are many reasons why someone might choose to undergo genetic testing. However, one of the main reasons someone will choose to do so is to diagnose any rare or inherited disorders that may have been passed down genetically from previous family members. Other reasons why someone may choose to go for genetic testing include:

1. Determining your risk of developing certain diseases, such as breast cancer

2. Helping doctors find out more information about your conditions to guide treatment decisions

3. Finding out the chances of having another child with the same genetic condition

4. Checking your eligibility to participate in clinical trials

Which diseases can genetic testing detect?

Genetic testing can detect a wide range of diseases, including:

• Hereditary disorders:

  • Cystic fibrosis

  • Huntington’s disease

  • Muscular dystrophy

• Cancers:

  • Breast, ovarian, colorectal, and other cancers linked to gene mutations (e.g., BRCA1/BRCA2)

• Neurological diseases:

  • Alzheimer’s disease

  • Parkinson’s disease

  • Amyotrophic lateral sclerosis (ALS)

• Cardiovascular conditions:

  • Familial hypercholesterolemia

  • Long QT syndrome

  • Hypertrophic cardiomyopathy

• Other conditions:

  • Sickle cell anaemia

  • Blood disorders like thalassaemia

  • Down syndrome (via prenatal testing)

What are some reasons I should undergo genetic testing?

Your doctor may recommend you consider genetic testing for a multitude of reasons, including:

• If your doctor suspects you have a health condition caused by genetic changes

• There is a family history of a genetic disorder or inherited cancer

• You or your partner wishing to know the risk of passing on a genetic condition to your children and want to assess your individual carrier statuses for certain diseases

• To learn whether you could have a child with a genetic condition when pregnant

• To understand and guide your cancer prevention or treatment plan

• You want to understand your risk for developing certain conditions later in life

If you face any concerns related to the above, do not hesitate to contact a specialist at Thomson Medical and discuss whether genetic testing is applicable for you. Request an appointment with Thomson Medical today.

What are the different types of genetic tests?

There are many different kinds of genetic tests, encompassing several types and each serving a specific purpose. There is no single genetic test that can detect all genetic conditions. 

Your healthcare provider can help you decide what genetic test is right for you based on your medical and family history and the condition for which you're being tested.

Carrier testing

If you have a family history of a genetic disorder such as sickle cell anaemia or cystic fibrosis, or if you're in an ethnic group that has a high risk of a specific genetic disorder, you may choose to have genetic testing before having children. This test determines whether you possess a gene mutation that you could potentially pass on to your children, even if you don't experience any symptoms yourself. 

An expanded carrier screening test can detect genes associated with a wide variety of genetic diseases and mutations and help identify if either you or your partner are carriers for the same conditions.

Diagnostic testing

If you have symptoms of a disease that may be caused by genetic changes, sometimes called mutated genes, genetic testing can be used to confirm or rule out a suspected genetic condition. For example, genetic testing may be used to confirm a diagnosis of cystic fibrosis or Huntington's disease.

Newborn screening

This test is conducted shortly after birth to screen for genetic and metabolic disorders that can be treated early, such as phenylketonuria or sickle cell disease. This type of genetic testing is also the most common type of genetic testing.

Pharmacogenetics

If you have a particular health condition or disease, this type of genetic testing may help determine what medication and dosage will be most effective and beneficial for you.

Presymptomatic and predictive testing

If you have a family history of a certain genetic condition, such as different types of cancer, these tests assess the risk of developing it before symptoms appear. 

For instance, testing for BRCA mutations can determine the risk of breast cancer; testing for TGFBR2 mutations identifies the presence of tumours related to colorectal cancer.

Preimplantation testing

Used during in vitro fertilisation (IVF), embryos are screened for genetic abnormalities before implantation, reducing the risk of passing on certain genetic disorders. Embryos without any abnormalities are then implanted in the uterus in hopes of achieving pregnancy

Prenatal testing

If you're pregnant, prenatal tests can detect some types of abnormalities in your baby's genes. Down syndrome and trisomy 18 syndrome are two common genetic disorders that are often screened for as part of prenatal genetic testing.

Traditionally, this type of analysis involves examining blood markers or conducting invasive tests like amniocentesis. A newer test called "cell-free DNA testing" looks at a baby's DNA via a blood test done on the mother.

How is genetic testing usually done?

Genetic testing typically involves collecting samples of blood, saliva, skin, amniotic fluid or tissue.  Therefore, based on the test type, a laboratory collects the sample and analyses it to search for specific genetic changes. The sample type required usually depends on the test being performed and the condition being investigated.

How can I prepare for the test?

Preparation for a genetic test is usually minimal and dependent on the type of test. Usually, you will not need to fast; just remember to wear comfortable clothing, hydrate and follow the necessary protocols when instructed, especially if the doctor is taking a blood sample or doing a tissue biopsy. Your doctor will advise you accordingly if special preparations are required.

Other than that, before going for genetic testing, remember to discuss with your doctor or genetic counsellor to understand the implications of the test. Please ensure you have a comprehensive account of your family's medical history. Your family medical history will help your doctor understand your risk for certain medical conditions better.

What is the procedure of getting a genetic test like?

The procedure will depend on the type of genetic testing you are getting. Each type involves a different sample collection method, such as:

• Blood sample:

  • A doctor will take the sample by inserting a needle into a vein in your arm. For newborn screening tests, a blood sample is taken by pricking your baby's heel.

• Cheek swab:

  • For some tests, a swab collects a saliva sample from the inside of your cheek for genetic testing.

• Amniocentesis

  • In this prenatal genetic test, it will be an invasive test. Your doctor inserts a thin, hollow needle through your abdominal wall and into your uterus to collect a small amount of amniotic fluid for testing.

• Chorionic villus sampling

  • For this prenatal genetic test, it is considered invasive testing as well. Your doctor takes a tissue sample from the placenta. Depending on your situation, the sample may be taken with a tube (catheter) through your cervix or through your abdominal wall and uterus using a thin needle.

How do I interpret my results?

A team of specialists, typically comprising laboratory scientists, clinical geneticists, doctors, and genetic counsellors, interpret your genetic test results. Once the laboratory report is ready, the clinical experts will review your results in the context of your medical history, symptoms, and family background to determine what the findings mean for your health.

This multidisciplinary approach ensures that the results are accurately interpreted and that you receive appropriate guidance on the next steps, whether that involves further testing, potential medical treatments, or family planning advice.

If you have questions or need help understanding your results, your doctor or a genetic counsellor can explain them in detail and discuss their implications for you and your family.

FAQ

Are DNA tests and genetic tests the same thing?

Yes, in most contexts, DNA and genetic tests refer to the same process: analysing your genetic material to detect changes linked to health, ancestry, or biological relationships.

Are DNA tests legal in Singapore?

DNA and genetic testing are legal in Singapore and are offered by various medical providers and laboratories. Certain types of testing, such as paternity or forensic tests, may be subject to specific regulations.

Which DNA test is the most accurate?

The accuracy of a DNA or genetic test depends on the condition being tested and the laboratory performing the analysis. Clinical-grade genetic tests performed in accredited medical laboratories are generally highly accurate for the conditions they assess.

How to do genetic testing in Singapore?

You can undergo genetic testing in Singapore through referral by your GP or specialist to a hospital or accredited laboratory. Some private clinics and hospitals also offer direct-to-consumer genetic testing services.

Can my GP perform a genetic test?

Your GP can refer you for genetic testing if there is a medical indication. The actual test is usually performed in a specialised laboratory, with the results interpreted by clinical genetics professionals.

Does Singapore have a DNA database?

Singapore maintains DNA databases for specific legal and forensic purposes, such as criminal investigations. These are separate from medical or consumer genetic testing databases.

What are the risks of DNA testing?

Risks are generally low but may include:

• Emotional impact of learning about genetic risks

• Privacy concerns regarding genetic information

• Potential implications for insurance or employment (depending on local laws)

• Uncertainty if results are inconclusive or reveal variants of unknown significance

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a specialist at Thomson Medical. Request an appointment with Thomson Medical today.