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What is Genetic testing?

Genetic testing is a type of medical test that identifies changes in chromosomes, genes, or proteins. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person’s chance of developing or passing on a genetic disorder. More than 1,000 genetic tests are currently in use, and more are being developed.

What is required for the test?

Testing is done by means of cheek (buccal) swabs. Buccal swab kits can be
requested from our laboratory or go to one of the clicks clinics we work with. It is
very little to no risk involved in taking a buccal swab.

Limitations of Genetics

Not all medication is covered in the gene test offered. However, the DNA test
we offer cover 74 markers on your DNA and is informative for a range of
medication related to cardiovascular disease treatment, antipsychotics and
antidepressants, oncology and pain medication.

Advantages of Genetic testing?

A sense of relief from uncertainty
In-depth knowledge about your risk
Information to help make informed medical and lifestyle decisions
Opportunity to help educate other family members about the potential risk

Genetic Test Variations

Breast, Ovarian and Prostate Cancer

BRCA1 and BRCA2 are major genes related to hereditary breast cancer. Women who have inherited mutations in these genes, have a high risk of developing particularly breast and ovarian cancer during their lifetimes. Male BRCA2 carriers are at an increased risk of prostrate and pancreatic cancer. Hereditary breast cancers tend to occur earlier in life than sporadic cases, occur more frequently in families and are more likely to involve both breasts. Founder mutations are common in specific populations, such as the Ashkenazi Jewish and Afrikaner populations.

Multiple endocrine neoplasia type 2 (MEN2) (tumours of endocrine glands):

MEN2 is an autosomal dominant predisposition cancer syndrome, affecting the endocrine system. It is characterized by tumours of the thyroid and adrenal glands. Three subtypes exist, including Familial medullary thyroid carcinoma (FMTC), all caused by mutations in the RET protooncogene.

PAI-1 Gene Mutation (coronary artery disease):

Variations in Plasminogen Activator Inhibitor (PAI-1) gene are associated with an increased risk for arterial and venous thrombosis, coronary artery disease and ischemic stroke.

Homocysteine (blood clots and cardiovascular disease):

Elevated levels homocysteine in the blood, caused by defects in the genes responsible for homocysteine breakdown, is a powerful risk factor for cardiovascular disease and thrombosis.

Familial hypercholesterolemia (high cholesterol):

Identification of individuals or families with a genetic predisposition to high levels of cholesterol, particularly LDL or “bad cholesterol”. Very common in the Afrikaner population in South Africa, affecting 1 in 80 people. This condition results in an increased risk for early cardiovascular disease.

Factor II (premature clotting in blood vessels):

Prothrombin thrombophilia is another inherited disorder of blood clotting, leading to an increased tendency to form abnormal blood clots in blood vessels. It affects approximately 1 in 50 people in the Caucasian population.

Apolipoprotein E-associated lipid disorders (clogged arteries):

Lipid and lipoprotein abnormalities are extremely common in the general population and are regarded as a risk factor for cardiovascular disease due to the influence of cholesterol on atherosclerosis.

Factor V Leiden (venous thrombosis):

Factor V Leiden (R506Q mutation) is the most common genetic risk factor for venous thrombosis. It has also been associated with an increased risk of pregnancy loss.

African iron overload (AIO) (previously known as African siderosis):

AIO occurs in as many as 10% of individuals of African descent. It is characterized by the accumulation of large amounts of iron in the reticuloendothelial cells of the liver, spleen and bone marrow as well as in hepatocytes.

Hereditary Haemochromatosis (HH) (iron overload disorder):

HH is characterized by progressive iron overload, with the main feature being excessive absorption of dietary iron. Early symptoms of HH are nonspecific and may include fatigue, joint pain, abdominal pain, and loss of sex drive. Later signs and symptoms can include arthritis, liver disease, diabetes, cardiac abnormalities, and skin discoloration. If HH is diagnosed early, treatment is effective and many symptoms are reversible.

Crohn’s Disease and Ulcerative Colitis

The exact cause of this inflammatory disease of the intestines is still unknown, but the interplay of environmental factors in a genetically predisposed host is thought to initiate disease. Parents, siblings or children of people with CD are 3 to 20 times more likely to develop the disease.

Cystic Fibrosis (sodium channel pathology leading to build-up of mucus):

Cystic Fibrosis is the most common life-limiting autosomal recessive disorder in Caucasian populations. It is a multisystem disorder with variable clinical symptoms, but is usually characterized by the triad of: recurrent respiratory infections, pancreatic insufficiency causing malabsorption of nutrients and abnormally high sweat chloride levels.

Alpha-1 antitrypsin deficiency (glycoprotein deficiency affecting lungs and liver):

It is an inherited disorder that may cause lung disease and liver disease. The earliest symptoms of Alpha-1 antitrypsin deficiency usually occur between the ages of 20 to 50 and include: shortness of breath, reduced ability to exercise, and wheezing.

Cystic Fibrosis (sodium channel pathology leading to build-up of mucus):

Cystic Fibrosis is the most common life-limiting autosomal recessive disorder in Caucasian populations. It is a multisystem disorder with variable clinical symptoms, but is usually characterized by the triad of: recurrent respiratory infections, pancreatic insufficiency causing malabsorption of nutrients and abnormally high sweat chloride levels.

Tay-Sachs disease (mental and physical deterioration):

Tay-Sachs disease is an inherited neurological disorder that progressively that severely affects the nervous system, leading to mental and physical deterioration. Although rare in the general population, it is common in the Ashkenazi Jewish population.

Friedreich’s Ataxia

Friedreich’s ataxia is the most common inherited ataxia. It is an autosomal recessive inherited disease of the nervous system, causing a loss of muscle coordination that gradually worsens over time.

Duchenne and Becker Muscular Dystrophy (progressive muscle weakness):

Duchenne Muscular Dystrophy (DMD) is the most common and severe form of childhood muscular dystrophy, affecting approximately 1 in every 3500 male births. BMD is clinically similar to DMD, but milder. Both conditions are inherited in an X-linked recessive manner and are caused by mutations in the dystrophin gene.

Myotonic dystrophy (wasting of the muscles):

Myotonic dystrophy is the most common heritable neuromuscular disorder. It is inherited in an autosomal dominant manner and is characterized by progressive muscle wasting and weakness, particularly in the lower legs, hands, neck, and face.

Variegate porphyria (photosensitivity and neurovisceral symptoms):

It is an autosomal dominant inherited disorder of porphyrin-heme metabolism. Manifestations may include skin photosensitivity, systemic symptoms arising from neurologic symptoms, or both. Variegate porphyria is most common in the Afrikaner population of South Africa; about 3 in 1000 people in this population have the genetic change that causes this form of the disorder.

Nonsyndromic Deafness:

The majority of cases of genetic deafness (70 percent to 80 percent) are nonsyndromic, i.e. hearing loss that is not associated with other signs and symptoms.

Hirschsprung’s disease (congenital aganglionic megacolon):

Hirschprung’s disease is an important genetic cause of functional intestinal obstruction. RET mutations have been shown to account for 40-50% of familial cases and 15-20% of sporadic cases.

Lactose intolerance:

It is the inability to metabolize lactose, because the required enzyme lactase is absent in the intestinal system or its availability is lowered. The frequency of decreased lactase activity ranges from as little as 5% in northern Europe, up to 71% for Sicily, to more than 90% in some African and Asian countries.

FAQs

frequently asked questions related to Pharmacogenetics

WHAT IS GENETIC TESTING?

Genetic testing is a type of medical test that identifies changes in chromosomes, genes, or proteins and is used to find changes that are associated with inherited disorders. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person’s chance of developing or passing on a genetic disorder. Several hundred genetic tests are currently in use, and more are being developed.

Genetic testing is voluntary and has many benefits but there are limitations as well.

HOW DOES GENOMICS INFLUENCE MY HEALTH?

Genomics plays a part in most of the leading causes of death. The study of genomics helps us find out why some people get sick from certain infections, environmental factors, and behaviors, while others do not. By understanding the interactions between gene, behaviour and the environment, we can find better ways to improve health and prevent diseases.

WHAT IF I ALREADY KNOW I HAVE A FAMILY HISTORY OF A DISEASE LIKE CANCER?

Genetic testing for hereditary diseases helps you and your doctor understand your true risk so you can make the best choices for preventative medical care. Knowing your family history is a very important first step, but genetic testing provides a more accurate assessment of your inherited risk.

IF GENETIC TESTING IS SO VALUABLE, WHY HAVEN’T I HEARD OF IT?

There is no question that genetic testing is the most accurate way of determining a patient’s risk of developing an inherited disease. However, many doctors, especially those who see patients for a wide range of conditions, may not yet have information on the very latest genetic testing options for their patients. You or your doctor can contact us for more information.

ARE THE GENETIC TESTS OFFERED BY GENEDIAGNOSTICS COVERED BY MEDICAL AID?

Some tests are covered by medical aid and the list is expanding. Please contact us for information on any specific test.

WHAT HAPPENS TO MY GENETIC TEST RESULTS?

Genetic test results are strictly confidential. GENEDiagnostics only release test results to the individual or doctor who ordered the test. Even when insurance plans pay for testing, the medical aid does not receive the results. Under no circumstances will GENEDiagnostics give patient results to any other party without the written consent of the patient.

WHAT ARE THE CHANCES THAT MY CHILDREN AND/OR FAMILY MEMBERS HAVE THE CONDITION?

If someone in a family has a disease the other members have a higher chance of carrying that gene relative to the normal population risk. Diseases are generally not just a result of one factor but rather the result of interactions of genes with your lifestyle (diet, exercise, smoking and drinking) that can be changed.

Some diseases result because a single gene is altered or missing (including hemophilia, cystic fibrosis, muscular dystrophy, and Huntington ‘s disease) and are called “single gene disorders. In this case genes play an extremely important role in determining whether or not a family member will also have the condition.

In these cases, family inheritance plays a much greater role in determining whether or not the condition is passed on. In these cases, behavioral and environmental factors don’t have a big effect on the disease but may improve someone’s quality of life. Speaking with your doctor or one of our preferred genetic counsellors is the best way to learn about your condition and its effect on your relatives.

ARE TESTS CONVENIENT?

Samples are stable for up to one week provided the swab was dried properly at room temperature and exposure was kept between 20°C and 37°C.

HOW ACCURATE IS THE TEST?

We have over 20 years experience in the industry and our laboratory is ISO compliant. Results are checked and rechecked to ensure that you can have absolute faith in the end product.

ARE TESTS PRIVATE?

Genetic results are governed by extremely strict laws and treated with strict confidentiality. Results are not given to any other third party.

WHAT IS THE DIFFERENCE BETWEEN GENETICS AND GENOMICS?

Genetics is the study of DNA and their genes and the influence thereof on health and disease.

Genetics explains the way characteristics are passed down from one generation to another. Genes carry the instructions for making proteins, which in turn, direct the activities of cells and functions of the body that influence traits such as hair and eye colour.

Genomics is a term that describes the study of all the genes in an individual, as well as interactions of those genes with each other and their environment (e.g diet).

Advances in genomics enables screening for genetic mutations to identify a potential disease before symptoms appear.

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