What is Genetic Testing Used For?
Clinicians believe that a better understanding of why and how genetic mutations cause certain diseases and conditions is crucial for the improvement of genetic testing and greater accuracy in early clinical diagnosis of various medical diseases and disorders.
Genetic testing is carried out for a number of reasons and at various stages of life.
Perinatal genetic testing
Perinatal genetic testing allows adults, parents-to-be, and parents of newborns to check for genetic abnormalities i.e. to see whether their baby is likely to be born with a genetic condition, the pre-disposition for a disease or, in the case of newborn screening, has been born with a genetic mutation.
Types of perinatal genetic testing include:
- Preimplantation testing – genetic testing most commonly used during IVF. Embryos are screened for genetic abnormalities which may affect their viability and pregnancy outcomes.
- Prenatal testing – genetic testing carried out during pregnancy to determine genetic abnormalities. Most commonly, routine screening will be carried out to identify the genetic mutations that may cause Down’s syndrome, Edward’s syndrome and Patau syndrome, for example.
- Newborn screening – newborns can be tested for a number of conditions caused by gene mutations, such as congenital hypothyroidism, sickle cell disease or phenylketonuria (PKU). If a condition is identified, treatment can begin immediately.
Types of prenatal genetic testing
Prenatal genetic testing (testing which takes place during the pregnancy) can be carried out in a number of ways. Research into prenatal genetic testing is ongoing and the types of test available to you will depend on a number of factors including whether you are able to afford private healthcare screening.
Types of genetic screening during pregnancy include:
- Alpha-fetoprotein (AFP) test or multiple marker test
- Amniocentesis
- Chorionic villus sampling
- Non-invasive prenatal testing (NIPT) (cell-free fetal DNA testing)
- Percutaneous umbilical blood sampling (withdrawing a small sample of the fetal blood from the umbilical cord)
- Ultrasound scan
If a whole gene needs to be tested for abnormalities, gene sequencing may be required. This is a delicate, precise process that takes longer than many other hospital laboratory tests. When a specific mutation is being looked for, it can take weeks or even months before conclusive results are available.
What’s more, genetic testing does not always provide definitive answers; the presence of a certain mutation may not mean there is 100% probability that a disease or disorder will occur. Sometimes further testing is required and sometimes only time will provide the answer.
Prenatal screening can lead to difficult decisions, such as whether to undergo amniocentesis. Depending on the results of genetic testing, there may be further decisions to be made about continuing or ending the pregnancy.
Other types of genetic diagnostic testing
Genetic testing can be used at any stage of life, the various testing scenarios include:
- Predisposition testing – This helps people to find out how susceptible they are to developing a disease such as cancer because of their genetic makeup.
- Pre-symptomatic testing – If a healthy person has a family history of a particular disease, genetic testing may be able to anticipate diagnosis of a condition before symptoms emerge.
- Symptomatic – When an individual shows certain symptoms, this type of test can help to identify or rule out specific genetic disorders. Both genes and chromosomes could be tested to check for abnormalities.
- Therapeutic – Genetic testing used to enhance drug therapies based on a patient’s genotype and related knowledge of drug efficacy or toxicity. For example, genetic testing in cell therapy ensures the integrity of stem cells before implantation. In transplantation medicine, tests are used to confirm compatibility of donor and recipient.
As new technologies are developed and the cost of gene sequencing comes down, genetic testing may become more affordable and be available for more and more patients and healthy people alike.
Next-generation sequencing (NGS) technologies are being developed to help laboratories produce large amounts of sequencing data from multiple samples. Previous methods were only able to sequence a single DNA fragment at a time, while NGS is able to sequence millions of fragments per run.
