Genetic testing in Kenya
THE STANDARD INSIDER
By Yvonne Kawira and Allan Mungai
| July 20th 2020
Seven years ago, doctors told her that she had a 87 per cent chance of developing breast cancer and a 50 per cent risk of ovarian cancer. Angelina Jolie, the American actress, had had a genetic test that showed that she carried the BRCA1 gene, a mutated inherited gene that increases a woman’s risk of ovarian and breast cancer. Her decision to get the test done was precipitated by the fact that her family had a long history of ovarian and breast cancer. Armed with the worrying information, she decided to get a preventative double mastectomy. About two years later, she had her ovaries and Fallopian tubes taken out to reduce her chances of developing ovarian cancer.
Genetic testing has since then become a pursuit for many. And in Kenya, the practice is catching on.
“More people are now seeking genetic tests because of the increasing awareness on health issues. That said, more education to the public needs to be done so that they can know why they are important,” says Andrew Kilui, a molecular biologist at Massive Genomics, one of the few centres that offer the tests in Kenya.
Genetic testing as a diagnostic tool identifies any peculiarities in your DNA. The tests performed are intended to confirm or rule out a suspected genetic condition or help determine a person’s chance of developing or passing on a genetic disorder.
Dr John Kiiru, a molecular biologist with KEMRI, confirms that it is now possible to conduct early and accurate screening for breast and colorectal cancer by screening for particular genetic markers. In his study, published in 2015, he noted that genetic results can help detect late-onset disorders, which include adult-onset diseases such as Huntington’s disease, cancer and heart diseases. He was, however, quick to point out that while a genetic test can show that you are likely to develop a condition, it is not a conclusion that it will definitely develop.
“Some of these diseases are complex and have both genetic and environmental causes, and the genetic result only gives an idea of possible predisposition to the condition and not a confirmation that such a condition will develop,” he said.
Using blood or saliva sample, a couple can find out if they carry genes that could cause diseases that could be passed on to their children. Genetic testing is now popularly used by couples to check for conditions that one is likely to pass on to their offspring. You may not have the condition yourself, but have the gene. In this case, you are a carrier. A carrier screening test will tell you if you or your partner are carriers and the chances of passing them on to children.
“Couples then can reach a decision to either not have babies, not get married, or make a conscious effort to learn what caring for such a baby can entail before committing,” says Angus Nassir, a biomedical scientist with Massive Genomics.
This is especially in the cases of:
· Sickle cell anaemia: Red blood cells have a crescent shape. This causes chronic anemia and episodes of pain. It is common in Coast region and Western Kenya.
· Thallasemia: A blood disorder where one carries fewer red blood cells. It also makes one prone to heart diseases that can greatly reduce one’s life span.
· Tay Sachs disease: Causes mental disability, blindness, seizures, and death, usually by age five.
· Fragile X Syndrome: Causes mild to severe learning disability.
· Spinal Muscular Atrophy. Studies show it is the leading cause of death in infants. It affects the spine, causing muscle weakness and robbing one of ability to walk, talk and eat.
· Cystic fibrosis: Causes problems with breathing and digestion.
These are serious diseases that can affect one’s lifespan and quality of life.
At age seven, Etemesi Ochola underwent a genetic test to determine his chances of exposure to sickle cell anaemia. At this point it showed that he already had the condition.
“My parents are both carriers of a gene. But they did not know this. Also, they did not undertake any tests. Had they conducted genetic tests beforehand, they would have been informed of a possibility of their children being born with this condition.”
And while he also did not get his spouse tested for the gene before they conceived their son, Etemesi now wants his son screened for the condition.
“This will inform our next cause of action, depending on the results,” he says.
Premarital screening can also detect male infertility.
“The tests can even be used to determine whether the man has a congenital syndrome that makes him infertile and the partners can make a marriage decision based on this,” says Nassir.
Prenatal genetic test
Down Syndrome is the most common genetic disease screened for using prenatal diagnosis. The tests are usually done when a mother is pregnant, to detect if the foetus has some conditions. The tests are done on cells from the foetus or the amniotic fluid. Medical advances have made it possible to have some tests done on a sample of the mother’s blood. Often done in the first trimester, or early second trimester, prenatal genetic tests commonly check for:
· Down Syndrome: This causes abnormal features of the face and body, heart defects, and mental disability.
· Edward Syndrome (Trisomy 18): It causes the baby to have a small head, heart defects and deafness.
· Spine problems
· Brain problems
In the case of spine and brain problems (spina bifida) the medic does an amniocentensis. This is where they take a sample of amniotic fluid and do an assessment.
In places like California, getting tested for Down Syndrome when pregnant is standard and covered by insurance.
There has, however, been controversy over prenatal diagnosis of a foetus over the action some pregnant mothers might take after finding out that their foetus is predisposed to a genetic condition.
Parents can decide to get their new born child tested as a preventative health measure. The tests are done to check the presence of metabolic diseases in newly born infants. It is performed immediately after birth before the baby leaves the hospital. Metabolic conditions detected in newborns are genetic conditions that affect the ability of the body to process the essential substances needed by the body to survive. An example of such a condition is phenylketonuria or PKU.
“Most of these tests usually have clear benefit to the newborn because treatment is available,” says Dr Kiiru.
“Babies with PKU are unable to break down an amino acid called phenylalanine and as a result this amino acid builds up in the body and can cause irreversible brain damage and intellectual disabilities, short stature, seizures and tremors, growth and failure to thrive.” Nassir adds.
Detection at birth enables the baby to lead a normal life as treatment is initiated upon detection. Treatment involves avoiding foods containing the amino acid phenylalanine such as eggs, fish, cheese, pork, milk, among others. Besides PKU, the newborn screening test can pick 71 other conditions such as galactosemia (inability to process foods containing galactose), homocystinuria, sickle cell disease, among others.
Genetic testing for cancer
Through some genetic tests, you can find out if you are likely to develop some cancers. The tests determine the presence of genes responsible for development of cancer.
“The method utilises next generation sequencing methods to detect the presence of genetic mutations associated with cancer,” says Nassir
Does it really help to know?
“Knowing one’s cancer risk allows them to lead a lifestyle that will lower their odds of getting disease. It also allows them to be more vigilant and commence treatment as soon as any sign of growth is detected, which, of course, improves their prognostic outcomes,” he says.
A study published in the ‘Journal of the American Medical Association’ shows that having the BRCA1 mutation increased the risk of breast cancer by 72 per cent and 44 per cent for ovarian cancer, while a BRCA2 mutation showed a risk of 69 per cent for breast cancer and 17 per cent for ovarian cancer. Men with the mutated genes have a higher than average lifetime risk for breast, prostate and other cancers. Like Angelina Jolie, the knowledge of whether they carry the gene has led to some decisions such as prophylactic mastectomy and oophorectomy (removal of the ovaries). However, doctors note that such procedures may reduce but do not necessarily eliminate the risk of cancer.
You can consider genetic screening for cancer if:
· You have had many first-degree relatives with cancer. These include your parents, siblings and children.
· You have relatives on one side of the family with the same type of cancer.
· A family member has more than one type of cancer.
· In your family, you have had many develop cancer at an earlier age than is typical. For example, breast and prostate cancers are more common among women over age 50.
. A genetic test by one or more relatives revealed a mutated gene.
. One or more family members have already had genetic testing that found a mutation.
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