Why Would a Doctor Order Genetic Testing?

Genetic testing is a process that usually involves sampling an individual’s DNA, including their genetic and chromosomal information, in order to understand if they are the carrier of a genetic mutation that might cause a rare disease in themselves or their children. It can also identify if someone is at risk of developing a rare disease due to an identified gene mutation or change, or if someone actually has a rare disease or genetic syndrome.

Why would a Doctor order genetic testing for an individual or a family?

Sometimes a doctor may order genetic testing for a patient, above and beyond standardized testing that takes place both prenatally and antenatally. Genetic screening and genetic testing for Down syndrome, is a standard part of prenatal care for women in the developed world, however sometimes a doctor may suggest further testing based on several factors. 

Family Medical History

If there is a diagnosis of rare disease in a family that affects a first degree relative, either a parent or sibling, then a doctor will recommend genetic testing both prenatally and antenatally for any future children. 

This recommendation will depend on if the rare disease is inheritable. Some rare diseases occur due to spontaneous genetic mutations during conception, and if a rare disease diagnosed in a family is caused by a de novo or new mutation, so genetic testing will not automatically be recommended.

However for a rare disease in a family with an inherited cause, a doctor will recommend genetic testing of all first degree relatives, in order to understand if the syndrome was inherited from a parent and how. They will more than likely order carrier screening for the parents. 

If one or both parents are carriers of a gene mutation that is known, a doctor will order genetic testing in some cases, for their unborn and born children. This will depend on the mutation one or either parents carry, and if this gene mutation can be inherited in a way which will cause a rare disease in a parent’s offspring. 

Some rare diseases are caused by genetic mutations that just one parent passes on, others require both parents to pass on the mutation. But genetic testing will be recommended either way, in order to understand if future children are also carriers of the same gene changes. 

If there is a pattern of unique symptoms within a family, with no known or clear medical cause, a doctor might order genetic testing, either to confirm or rule out a rare disease as the cause. Similar sets of symptoms throughout several generations of a family, might suggest an inherited cause, and genetic testing might be able to provide greater clarity on this. The type of symptoms will affect which type of genetic testing a doctor will order. 

Unique symptoms

Because genetic syndromes can be caused by a spontaneous and new gene mutation, and are not always inherited, even unique symptoms in just one member of the family might lead a doctor to recommend genetic testing for the individual concerned. 

Many rare diseases present with a set of unique symptoms, and if a doctor believes in a link between these in a patient and a rare disease, they may order genetic testing. 

Previous genetic screening is inconclusive or identifies cause for concern

Sometimes a doctor may order DNA testing, if previous genetic screening or testing returns a result that is unclear or if it identifies possible higher risk for a rare disease. Further and more specific genetic testing might be ordered in order to understand better the cause or exact risk. 

Screening for Down syndrome in the first trimester of pregnancy can identify the possible risk of a baby being born with Down syndrome, but can not provide a definitive diagnosis. If this screening reveals that a baby appears to be at high risk for being born with down syndrome, so a doctor may order a type of genetic testing known as amniocentesis. This is an invasive process which involves taking a sample of amniotic fluid from around the baby and testing it. This type of genetic testing is very accurate when diagnosing Down syndrome. 

In the case of misdiagnosis

If a doctor suspects that a patient has been misdiagnosed or received a wrong diagnosis for a genetic syndrome, they may order further genetic testing. This testing should be more in line with the patient’s family medical history, and symptoms, and should aim to provide a more accurate diagnosis. 

Genetic testing and genetic counseling

No doctor should order genetic testing for a patient or family, without first referring them to genetic counseling. Genetic counseling is an essential service, both as a support and medical service, for families undergoing any type of genetic testing, and for any reason.

Genetic counselors are able to walk families through recommendations for genetic testing, what each test will entail, and what the results of said testing might be. 


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