Whenever someone hear the word “Genetic Testing” from a doctor, a question may popup to mind. What are the different types of Genetic Testing? Is there only one type of genetic testing for all diseases or are there several types?
Well, this article helps you understand all about the Types of genetic testing available for different specialties.
The understanding of genetic testing is done primarily on the basis of two factors: Technology used or Disease Category. Currently, we will focus on types of genetic testing based on Disease Category.
There are many types of genetic testing available for pregnant or expectant mothers to check and confirm the well being of child. It depends when the genetic test is required.
- Non-Invasive Prenatal Test (NIPT)– It is the most common prenatal test done during 9-13 weeks of pregnancy to rule out common genetic abnormalities such as Down’s Syndrome, Trisomy 21, 18 and 13 etc. Different companies offer different combinations of genetic disorders under this test. However, the number of diseases is limited to around 5-10. You can read more about it on article on
- Carrier Screening– It is a type of genetic test in which many thousand genes are clubbed together to screen the expecting mother and father to check, if they are carrying any dangerous genetic mutations. If both mother and father are found to be “carrier” of same genetic mutation, there are high chances that their child will suffer from the disease. It is usually recommended if there is any known family history for genetic disorders in family of mother and father. You can read more about it on our article on Carrier Screening.
- PGS/PGD– These are short form of Pre-Implantation Genetic Screening and Preimplantation Genetic Diagnosis, respectively. PGS/PGD are a type of genetic tests done prior to zygote selection for implantation during IVF treatment. It helps in screening the best zygote, which is free from all genetic abnormalities. PGS is a screening test for unknown genetic disorders while PGD is a confirmatory test if prior information is available of the genetic mutation in parents (Egg and Sperm donors)
- Single Gene Mutations Test– This category of test is offered by different names by different companies. Basically, this test is used to confirm presence or absence of known mutations only. The mutations are usually already identified by other technologies in different family member. Single Tests can either target a specific mutation or many nearby known mutations such as in the case of Beta Thalassemia, which has many mutations in a single gene.
- Amniocentesis– It is a diagnostic confirmatory test for confirmation of chromosomal aneuploidies in foetus. It is highly risky invasive procedure and now mostly substituted by NIPT. However, if a NIPT test is unclear, doctor may advise to go for amniocentesis.
- New Born Screening – This is another kind of genetic test used to check the health of new born babies. It screens the sample for most common disorders of metabolism and/or common genetic disorders which might have not been checked during pregnancy.
- Cancer Panels– Commonly used to assess risk of developing a cancer, the Cancer Panels offer screening of 40-500 or more genes which are associated with development of certain cancers. These panels can include:
- Hereditary Cancers Panels to check for mutations in genes associated with hereditary cancer such as Breast and Ovarian Cancer, Colon Cancer etc.
- Somatic Cancer Panels– to check for mutations that are not inherited from patients but arise during the lifetime of the patient such as some of the Blood Cancers, Lung cancers etc.
- Therapy Panels– These genetic tests screen for mutations in certain genes which affects a patient’s response to anti-cancer drugs. Absence or presence of certain mutations can change the out of patient’s anti-cancer therapy as favourable or unfavourable.
- Single Gene Mutations Test– Many times, the specific mutation is known, or the likely gene is known if a doctor can pinpoint the cancer type and therapy. Instead of going for expensive panels, doctors may advise to go for single gene tests such as BCR-ABL for Leukaemia and KRAS, BRAF etc.
A vast number of genetic disorders are inherited and passed from generations to generations. Inherited Disorders genetic testing can be easily done by especially curated Multi Gene panels or Single Gene Tests using up to 2-3 different technologies. Most Common inherited disorders include Heart Diseases, Obesity, High Blood Pressure etc.
Few genetic disorders which are caused due to a mutation in mitochondrial genome (Yes, Mitochondrial has its own genome different from our main DNA) are usually detected by Mitochondrial Sequencing Panels. These panels are useful as the sequence complete mitochondrial genome and may even tell if a patient has got the disease from his/her mother.
It is a kind of Genetic test which is used to establish paternity claims. It matches the DNA of a sibling to those of parents to check if a parent is actually a biological parent or not. It is commonly used to settle legal disputes among child and parents.
Clinical Exome/ Whole Exome/Whole Genome
This are genetic tests which basically can be used for every genetic disorders apart from mitochondrial genetic disorders.
The Clinical Exome contains 5000 to 7000 genes are known to be “clinically relevant”. These genes have mutations which have good scientific support to claim their effect in development of genetic disorders.
Whole Exome on the other hand contains all approx. 22000+ human genes. Whole Exome genetic test contains all gene whether they are confirmed to be associated with genetic disorders or not. Since the research behind genetic disorders is still going on and new mutations are discovered regularly in new genes, many times Whole Exome is a good choice for doctors in cases where the genetic disorder identification is not possible by routine testing.
Whole Genome, although rarely used, are used for screening full genetic DNA of any patient. This is used when all other genetic testing options have failed. It is still quite expensive so not recommended to everyone.
Clinical Exome and Whole Exome can be used for identification and screening of genetic disorders under following categories:
- Neuro-Muscular Disorders affecting nervous system and muscles.
- Brain Disorders such as Epilepsy and Autism
- Heart Disorders etc
The list is not complete as there are many other genetic disorders which can be checked by clinical exome and whole exome.
This article is intended to provide an overview of the various types of genetic testing options available. Anyone looking to take a genetic test should always consult a certified genetic counsellor or their doctors, who will suggest the best option suitable for them. Although Genetic Testing is now available as direct to consumer for many diseases, it is still a complex test with reports not understandable easily and its interpretation requires high expertise in genetic diseases. Therefore, individuals should avoid to go for such tests without approval from their doctors.
Please comment for any suggestions or feedback!