Hearing the words �genetic testing� can bring up many questions.
Why has my doctor recommended this test? What will it tell us? Does a positive result mean I definitely have a disease? What if the result is negative? Could the result affect other members of my family?
For patients and caregivers dealing with an unexplained or rare condition, genetic testing can sometimes be an important part of the diagnostic journey.
But genetic testing is not a single test�and it is not appropriate for everyone.
Understanding what genetic testing means, when it may be considered and what its results can and cannot tell us can help patients and families make more informed decisions.
What is genetic testing?
Genetic testing looks for changes in a person's DNA that may be associated with a particular health condition.
DNA contains the instructions used by our bodies to develop and function. These instructions are organized into genes and chromosomes.
Changes in DNA are common. Many have no known effect on health. Others may contribute to a person's risk of developing a disease or may be responsible for a genetic condition.
Genetic testing can look for different types of genetic changes depending on the medical question being asked.
The National Human Genome Research Institute (NHGRI) explains that genetic testing can be used for several purposes, including diagnosing disease, identifying genetic changes that may increase disease risk and providing information relevant to family members. (genome.gov)
In simple terms:
Genetic testing asks whether there are particular changes in a person's genetic material that may help explain a health condition or provide information about future health.
Is genetic testing the same as a test for rare diseases?
No.
There is no single genetic test that can identify every rare disease.
Some rare diseases are caused by genetic changes, while others may have non-genetic causes. Even when a disease has a genetic basis, the relevant genetic change may be difficult to identify or may not yet be known.
The type of genetic test selected therefore depends on the patient's symptoms, medical history, family history and the condition being investigated.
This is why genetic testing is generally most useful when it is guided by an appropriate clinical assessment.
When might a doctor recommend genetic testing?
There are many situations in which a healthcare professional may consider genetic testing.
1. When a rare or inherited disease is suspected
If a patient's symptoms, physical findings, laboratory results or family history suggest a genetic condition, a doctor may recommend genetic testing as part of the diagnostic evaluation.
For example, testing may be considered when a patient has a combination of unusual symptoms that cannot be adequately explained by more common conditions.
A genetic diagnosis can sometimes provide an explanation for symptoms that have remained unexplained for a long time.
However, testing should not be viewed as a substitute for a medical evaluation.
2. When there is a family history of a genetic condition
A known genetic condition in a family may lead healthcare professionals to consider testing other relatives.
The exact approach depends on the condition and how it is inherited.
For some inherited conditions, knowing whether a person carries a particular genetic change can provide useful information about their own health or potential implications for their children.
Genetic counselling can help families understand these possibilities before and after testing.
3. When a child has unexplained developmental or medical problems
Genetic testing may sometimes be considered when a child has unexplained developmental differences, intellectual disability, multiple congenital abnormalities, seizures or other features that suggest a possible genetic condition.
The appropriate test depends on the child's clinical features.
In some cases, broader genomic testing may be considered when a specific genetic condition cannot be identified from the clinical presentation alone.
The American College of Medical Genetics and Genomics has issued evidence-based recommendations concerning the use of exome and genome sequencing in pediatric patients with congenital anomalies, developmental delay or intellectual disability. (pubmed.ncbi.nlm.nih.gov)
4. To confirm a diagnosis
Sometimes a doctor already has a strong suspicion of a particular genetic condition.
A targeted genetic test may then be used to look for the specific genetic change associated with that condition.
If the relevant change is identified, the result may help confirm the diagnosis.
A confirmed diagnosis can be valuable because it may help guide medical management, monitoring and discussions about the condition's inheritance.
What are the different types of genetic tests?
The phrase �genetic testing� covers several different approaches.
Targeted testing
A targeted test looks for a specific genetic change or a specific condition.
This may be appropriate when the healthcare team already has a particular diagnosis in mind.
Single-gene testing
As the name suggests, this examines one particular gene when there is a strong reason to suspect a condition associated with that gene.
Gene panel testing
A gene panel looks at multiple genes associated with a particular disease or group of related conditions.
This can be useful when several different genes could potentially explain a patient's symptoms.
Whole-exome sequencing
Whole-exome sequencing examines the protein-coding regions of many genes.
Because it looks much more broadly than a single-gene test, it may be considered when the cause of a patient's condition is unclear and a genetic explanation is suspected.
Whole-genome sequencing
Whole-genome sequencing examines a person's genome more broadly, including regions outside the protein-coding portions of genes.
It can provide a much larger amount of genetic information, but interpreting that information can be complex.
The appropriate test depends on the clinical question. More testing does not automatically mean better testing.
How is genetic testing performed?
Genetic testing usually requires a biological sample.
Depending on the test, this may be obtained from:
Blood
Saliva
A cheek swab
Other types of biological samples
The sample is sent to a laboratory, where DNA is analyzed using the method appropriate for the test.
The process may sound straightforward, but interpreting the result can be much more complicated.
A genetic test should therefore be considered as part of a larger clinical process rather than simply a laboratory report.
What can the results mean?
Genetic test results are not always simply �positive� or �negative.�
A result may indicate that a disease-causing genetic change was identified.
It may also show that no relevant genetic change was found.
Sometimes a test identifies a variant of uncertain significance (VUS). This means that there is not enough scientific evidence to determine whether the genetic change is related to disease.
The American College of Medical Genetics and Genomics and the Association for Molecular Pathology provide standards and guidelines for interpreting sequence variants, including the classification of variants based on available evidence. (pubmed.ncbi.nlm.nih.gov)
This is important because a VUS should not automatically be treated as proof that a genetic condition is present.
Genetic results require appropriate professional interpretation.
What does a negative genetic test mean?
A negative result does not always mean that a genetic condition has been completely ruled out.
There are several possible reasons.
The test may not have been designed to detect the particular type of genetic change involved. The condition may be caused by a genetic change that science does not yet fully understand. Or the underlying cause may not be genetic.
This is why doctors interpret genetic test results alongside symptoms, physical findings, family history and other investigations.
If the initial testing is negative but clinical suspicion remains high, a healthcare professional may sometimes recommend additional evaluation or reconsideration of the diagnosis.
Why is genetic counselling important?
Genetic information can have implications for more than one person.
A genetic diagnosis may raise questions about parents, siblings, children or other relatives.
Genetic counselling helps patients and families understand these implications.
According to the National Human Genome Research Institute, genetic counsellors help people understand how genetic conditions may affect them or their families and provide information about genetic testing and its potential implications. (genome.gov)
Genetic counselling may take place before testing, after results are available, or at both stages.
A genetic counsellor or genetics professional may discuss:
Why the test is being recommended
What the test can and cannot detect
Possible outcomes
Possible implications for family members
Limitations of the test
What different results might mean
Whether additional testing may be appropriate
This can help patients make informed decisions rather than approaching testing simply as a search for a �yes� or �no� answer.
Can genetic testing affect the whole family?
Sometimes.
If a genetic change associated with an inherited condition is identified, relatives may potentially benefit from discussing whether testing is appropriate for them.
However, family testing should not be done automatically.
The relevance of testing depends on the specific condition, inheritance pattern, age of the relative and other factors.
A genetics professional can help determine who may benefit from further evaluation.
What should patients ask before genetic testing?
If your healthcare professional recommends genetic testing, consider asking:
Why are you recommending this test?
Understanding the medical reason for testing is a good place to start.
What exactly will the test look for?
Different tests detect different types of genetic changes.
What could the result tell us?
Ask how a positive, negative or uncertain result might affect your care.
Could the result have implications for other family members?
This can be particularly important when an inherited condition is suspected.
What happens after the result?
Knowing whether you will receive genetic counselling or specialist follow-up can help you understand the next step.
How long will the results take?
Turnaround times vary depending on the laboratory and type of test.
Genetic testing is powerful�but it has limits
Genetic testing has transformed the diagnosis and understanding of many inherited and rare diseases.
But it is important not to view it as a perfect answer to every unexplained health problem.
A test can only detect what it is designed and technically capable of detecting. Scientific knowledge also continues to evolve.
Sometimes a genetic test provides a clear diagnosis.
Sometimes it provides a clue.
Sometimes it does not identify a cause at all.
And sometimes a result that is uncertain today may become easier to interpret in the future as scientific knowledge grows.
That is why genetic testing should be interpreted in context�not in isolation.
The most important thing to remember
If your doctor recommends genetic testing, you do not need to understand genetics before you have the conversation.
Start with simple questions:
Why is this test being recommended?
What are we looking for?
What could the results mean?
What happens after the result?
The goal of genetic testing is not simply to generate a laboratory report.
For some patients, it can help explain a long-standing medical mystery. For others, it may help guide monitoring, medical care or family discussions.
And sometimes, even when a test does not provide an answer, it can help healthcare professionals decide what to investigate next.
At Healing Wings Foundation, we believe that patients and caregivers deserve clear, understandable information about the medical processes they may encounter during a rare disease journey.
Genetic testing can be complex�but understanding the basics can make the conversation with your healthcare team a little easier.
Because informed patients are better equipped to ask questions, understand their options and participate in decisions about their care.
Medical Disclaimer
This article is intended for general educational and awareness purposes only. It does not constitute medical advice, diagnosis or treatment and should not be used as a substitute for consultation with a qualified healthcare professional.
Genetic testing is not appropriate for everyone and cannot detect every genetic or rare disease. The type of test, interpretation of results and clinical significance vary depending on the individual and the condition being investigated. Genetic test results should be interpreted by appropriately qualified healthcare professionals in the context of the patient's medical history, clinical findings and other relevant investigations.
Patients and caregivers should discuss the potential benefits, limitations and implications of genetic testing with their healthcare team and, where appropriate, a qualified genetic counsellor or genetics professional.
