Fertility Treatments

Genetic Testing

It is a type of medical diagnosis and screening test that looks for changes in chromosomes, genes, and proteins before, after, and during pregnancy.

Introduction To Genetic Testing

A form of medical diagnosis and screening tests aimed at identifying any changes in chromosomes, genes, and proteins before, after and during the pregnancy is called genetic testing. 

The results of these diagnostic and screening tests can help you analyse the probability of a genetic medical condition and even help you determine if there is a possibility of that condition being passed on to the forthcoming child. The doctor may choose from more than 77,000 genetic tests, and the expert researchers are working tirelessly to develop more of them. 

A doctor may choose to perform genetic testing to analyse the changes in:

  • Chromosomes: The genetic tests used to identify changes in chromosomes, go through the long lengths of DNA, and whole chromosomes, to determine if there have been any significant genetic changes, like a copy of a chromosome. They also check if these changes have resulted in a genetic disorder.
  • Genes: The tests developed to analyse the genes go through the whole DNA sequences and identify any mutations or variations that may cause a genetic disorder or increase the risk of getting afflicted with it. The doctor may switch the scope of a gene test between narrow and large for analysing individual nucleotide or DNA building blocks, one or more genes, or a person’s genome. 
  • Proteins: The genetic tests also analyse the activity level exhibited by the enzymes or proteins. If there are abnormalities in either of the two, it may indicate some DNA changes which are likely to cause a genetic disorder. 

Opting for a genetic diagnostic or screening test is entirely up to you. As with any other test or treatment, genetic testing has both advantages and disadvantages. So whether or not you want to go for it is a personal decision and a rather tricky one at that. You may opt for a counselling session with a geneticist, who can provide you with detailed information about the advantages and drawbacks of genetic testing and discuss its physical, social, and emotional aspects. 

As we mentioned before, there are several types of genetic tests, which we will discuss in the next section.

Types Of Genetic Tests

The doctors may choose several types of tests to analyse your chromosomes, genes and proteins. They will take several factors into account while selecting the suitable test. These factors may include what kind of genetic condition(s) is suspected in the patient and what genetic variations these conditions may bring along. If the specialist can’t determine anything from the initial test, they may test to analyse several chromosomes or genes. But if the initial test suspects a particular condition, the doctor will proceed with a more specific test to pinpoint the issue. 

There are several types of genetic diagnostic and screening tests, including:

  • Chromosomal tests

The genetic tests used to identify changes in chromosomes, go through the long lengths of DNA, and whole chromosomes, to determine if there have been any significant genetic changes, such as missing or extra chromosome (also known as monosomy or trisomy, respectively), translocations or rearrangements of chromosome segments, etc. There may also be a large piece of missing or added (duplicated) chromosome. In addition, there are a few particular genetic conditions that are linked with chromosomal changes. If the doctor suspects one of these conditions, they may go for chromosomal tests. For example, deletion of a section of chromosome 7 may cause a condition called Williams syndrome. 

  • Biochemical tests

These types of tests don’t directly analyse a strand of DNA. Instead, they analyse the activity level exhibited by the enzymes or proteins produced by genes. Abnormalities found in the enzymes or proteins may indicate mutations and changes in DNA that may carry a genetic condition. For instance, biotinidase deficiency may be due to low levels of biotinidase enzyme activity. It may also be a result of BTD gene variants. 

  • Molecular tests

These tests usually look for the presence of one or more genes. They analyse the order of individual nucleotide or DNA building blocks in a patient’s genetic code. This process is known as DNA sequencing. Molecular tests vary according to the scope of analysis:

  • Single gene: These tests analyse a single gene for genetic variations. They can help a doctor either rule out or confirm a particular diagnosis if several genetic variants may be causing the suspected condition. 
  • Targeted single variant: These tests target a particular variant of a gene. That particular variant may be known to cause a certain genetic disorder. For instance, the HBB gene contains a specific variant that may cause sickle cell disease. The doctor may opt to perform this test on the patient’s family members to determine if they have the same gene variant and familial condition. When providing information about disease or health risk to the patient, the direct-to-consumer genetic testers usually analyse a few particular variants in the genes rather than all of them. 
  • Gene panel: This type of test checks for mutation in the variants in multiple genes. If a patient exhibits symptoms indicating several genetic disorders all at once, the doctor may go for a gene panel to identify a precise diagnosis. It may also be chosen if a doctor suspects a condition may be caused due to variants in several genes. For instance, epilepsy may be due to a number of genetic causes. 
  • Gene expression tests: This genetic test will analyse which genes are expressed (turned off or on) in different cells. mRNA molecules may be produced by the cells in the active state of a gene. The molecule may be a blueprint for protein production. These tests also determine the active genes in the mRNA in cells. Underexpression (too little activity) or overexpression (too much activity) may indicate a particular genetic condition like cancer. 

 

These tests are chosen according to the patient’s condition and several other factors, which the specialist will discuss during the consultation.

Various Uses Of Genetic Testing

Genetic screening and diagnostic tests can provide the doctor with detailed information about a patient’s genetics. Here are a few other uses of genetic testing concerning different techniques:

  • Diagnostic testing: The test is used to either rule out or pinpoints a particular chromosomal or genetic condition. The doctors use this test in several instances to certify the diagnosis in case of a suspected particular condition based on the exhibited signs and symptoms. It can be performed at any time during a person’s life or prior to birth, but it is not available for every genetic condition or gene. The results of this test can affect the patient’s healthcare and hygiene choices, along with the disorder management. 
  • Prenatal testing: This type of test is performed before birth to detect mutations in the chromosomes and genes of a fetus. The doctor may recommend prenatal testing to the patient if they suspect a chromosomal or genetic condition in the forthcoming baby. The test may help a patient lower the uncertainty and make informed decisions about pregnancy. However, it may not be able to identify every single congenital disability and hereditary issue.
  • Predictive and presymptomatic testing: The doctor may opt for this type of testing for detecting genetic mutations linked with conditions after birth, usually later in the patient’s life. The doctor may opt for this type of test for a patient with a family member suffering from a genetic condition. They may not have any symptoms or features of the said genetic condition. So it will help the doctor pinpoint the issue. Predictive testing may be advantageous to identify genetic mutations that raise the risk of genetics-based disorders like cancer. Then, there’s presymptomatic testing, which can help the doctor determine whether, in future, a patient will get affected with a genetic condition like hereditary hemochromatosis or iron overload disorder. It can help determine the presence of a disease before the patient exhibits any signs or symptoms. Both of these tests can help determine the risk of a person developing a particular condition to formulate a proper plan for medical care. 
  • Newborn screening: As the name suggests, this type of screening is performed on a baby just after they are born. This type of testing aims to determine the presence of any genetic disorder that the doctor can treat early in the baby’s life. Millions of babies are tested with newborn screening every year. Several experts in the field recommend trying at least 35 different medical conditions to ensure that the baby is healthy. 
  • Preimplantation testing: Also known as PGD or preimplantation genetic diagnosis, this specialised technique can help you bring down the risk of your expected child being born with a chromosomal or genetic condition. The doctor will determine any genetic mutations in the embryos created using artificial reproductive techniques like in vitro fertilisation with this testing method. IVF is a method that involves retrieving the eggs from a woman and fertilising them with the male partner’s or donor’s sperm to create an embryo in a fertility lab. A biopsy is performed on a tiny number of cells taken from the fertilised embryos for this testing. The embryos without any genetic mutations are processed for implantation into the woman’s uterine lining for initiating pregnancy. 
  • Carrier testing: With the help of carrier testing, the doctor will try to determine the presence of a copy of the genetic mutation in the patient, which is present in two or more copies, which may result in a genetic condition. This test is usually performed on people from a particular ethnicity with a risk for a certain genetic condition or the patients with a family member suffering from a genetic condition. By testing both parents, the doctor will be able to determine with abundant information the risk of their child being affected with a genetic disorder. 
  • Forensic testing: This type of test is quite different from the ones stated above. The forensic doctor uses it to identify a victim of a catastrophe or crime, determine the relationship between two people, and also rule out or identify a suspect. For example, it can help determine if a person is the father or mother of a child. 

The type of test required for a patient or their baby’s well-being will be determined by the patient after the initial consultation.

Genetic Testing Process

A healthcare provider will arrange the genetic testing process after you have your decision, which may be a part of the initial consultation. These tests are usually conducted on the patient’s hair, skin, blood, amniotic fluid (fluid surrounding your fetus during pregnancy), etc. For instance, the buccal smear is a process that uses a cotton swab or small brush for collecting tissue samples from inside their cheeks. Then a laboratory technician analyses the sample for mutations in DNA, chromosomes or protein, based on the suspected condition. After that, the technician will provide the patient’s doctor or primary caregiver with lab reports. 

For the newborn screening, the doctor will perform a test on the patient’s blood sample. Unlike other types of genetic screening and diagnostic tests, the patient will only receive a result if there is an issue. If there is an issue, and the test is positive, they’ll require additional testing to identify the genetic condition. 

Before having a genetic test, you may want to thoroughly understand the procedure, its advantages and drawbacks, and possible consequences. The doctor will explain these aspects to the patient and get informed consent. 

If you are looking for direct-to-consumer genetic testing, you may go directly to the testing company instead of visiting the doctor. After having this kind of testing, people tested positive will be at a higher risk of a particular genetic condition. If tested positive, you may want to consult your healthcare provider.

Benefits Of Genetic Testing

Whether you test positive or negative, there will be several benefits of genetic testing. Firstly, having conclusive test results will relieve you of any uncertainty and also help in making an informed decision about your health and hygiene. If you, fortunately, have received a negative test result, you won’t require any unnecessary additional screening tests and checkups. But in case of a positive test, you’ll have to go for additional prevention, monitoring and treatment techniques. In addition, newborn screening can help you determine the presence of a genetic disorder for starting the treatment.

Are There Any Risks And Limitations?

Well, the good news is that there are not many physical risks associated with genetic testing, especially the tests that require a buccal smear (a process that uses a cotton swab or small brush for collecting tissue samples from inside their cheeks) or a blood sample. One of the significant risks associated with genetic testing is a miscarriage or losing the pregnancy, usually due to prenatal diagnostic testing processes (called chorionic villus sampling and amniocentesis). That is because they require a tissue or amniotic fluid sample around the sample. 

Several risks associated with genetic testing usually have social, emotional or even financial consequences of the test results. There is a good chance you will feel depressed, guilty, angry or anxious about your genetic testing results. In certain instances, you may have a slight conflict with your family members due to the test results revealing sensitive personal information about you and your family member having the test. You may also face a slight worry about genetic discrimination in insurance or employment. 

One of the limitations of genetic testing is that it provides limited info about the genetic condition. These tests often can’t tell you the important information like symptoms of the condition you have been identified with, the severity of the symptoms, or whether or not that condition will progress with time. So it’s not really about the testing process, but there are not many techniques for treating the diagnosed genetic disorder. 

The doctor will explain to you all about the limitations and risks of the genetic testing techniques right at the time of initial consultation.

Genetic Screening Tests Vs Genetic Diagnostic Tests

There are two main types of genetic testing: genetic screening and genetic diagnostic. Genetic screening helps evaluate your risk of getting afflicted with a particular genetic condition. But genetic diagnostic tests help you identify a particular congenital disease. Both these genetic tests have their own advantages and drawbacks. 

A genetic screening test is usually considered for people who don’t exhibit symptoms of a genetic disorder. The test determines if the risk of you developing a particular genetic condition is higher or lower than average. A positive result for genetic screening would mean that you are more at risk of getting affected with a particular disease than average. On the contrary, if you have received a negative test, it would mean that the risk of you getting afflicted with a condition is lower than average. But these results are only estimated and not conclusive. So you may be at a higher risk of being afflicted with a genetic condition, even though you don’t suffer from it. It is called false positive. Likewise, you may be at a lower risk of being afflicted with a genetic condition, even though you do suffer from it. That is called a false negative. The doctor may suggest additional tests to be absolutely certain.

Examples of genetic screening include newborn screening and non-invasive prenatal screening/testing (NIPS/NIPT).

Genetic diagnostic tests are usually used in people exhibiting some signs and symptoms. So the doctor may use it to either certify or rule a particular condition that may be causing them. These tests can also tell you whether you are at risk of developing a particular condition and pass it on to your future offspring. This type of testing can be conducted anytime during a person’s life timeline, from before birth to any age. But diagnostic tests can be performed for every gene and every genetic condition. You can use the report of this test for choosing the best healthcare and hygiene approaches.

Examples of genetic diagnostic tests include chromosomal tests and molecular gene tests.

Conclusion

Genetic testing is a way of identifying mutations or changes in your DNA. The diagnostic approach can be quite beneficial in several areas of medicine and can help you change the approach for the medical care of you and your family. It can also help you determine if you are at risk of developing a particular genetic condition. These tests may be performed with the help of a blood sample or buccal smear. Genetic testing will also tell if you are at risk of being afflicted with a condition your family member suffers from. 

Please consult the Fertility experts at Siya Health, or call our Siya Fertility Counsellor today , if you are looking for genetic screening or diagnostic testing to identify the presence of a particular genetic condition.

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Dr. Dipesh Sorathiya

M.S. (Obs & Gyn)
DIP. in Gynec Endoscopy (CICE)

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