Genetic Testing vs Genetic Screening: What’s the Difference?
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| Genetic Testing vs Genetic Screening: What’s the Difference? |
Genetic testing and genetic screening are related terms, but they do not mean exactly the same thing. Both involve genetic information, yet they are used for different purposes.
In simple terms, genetic screening generally looks for people who may have a higher-than-average risk of a genetic condition, while genetic testing examines an individual's genetic material for specific changes or variants.
Understanding the difference is important because a screening result is not necessarily a diagnosis. A positive screening result may indicate that additional evaluation or diagnostic testing is appropriate.
What Is Genetic Testing?
Genetic testing is a laboratory-based process used to examine a person's genetic material for changes that may be associated with a genetic condition.
Depending on the test, scientists may examine individual genes, groups of genes, chromosomes, or much larger portions of the genome.
Genetic testing can be used for several purposes, including helping investigate a suspected genetic condition, identifying a genetic change associated with increased disease risk, or determining whether someone carries a particular genetic variant.
The Centers for Disease Control and Prevention explains that genetic testing looks for changes in DNA that may provide information relevant to medical care.
Examples of Genetic Testing
- Single-gene testing: Examines one particular gene.
- Genetic panel testing: Examines multiple genes associated with a condition or group of conditions.
- Exome sequencing: Examines the protein-coding portions of many genes.
- Whole-genome sequencing: Examines a much larger portion of a person's DNA, including most of the genome.
- Chromosome testing: Looks for larger changes involving chromosomes.
No single genetic test can identify every possible genetic condition. The appropriate test depends on the biological question, family history, symptoms, and other factors.
What Is Genetic Screening?
Genetic screening is generally used to identify people or groups who may have an increased risk of a genetic condition.
The National Human Genome Research Institute describes genetic screening as a way of identifying a smaller group within a larger population that may have a higher risk of having a genetic disease, developing one, or passing a genetic condition to offspring.
Screening can therefore be useful for identifying people who may benefit from additional evaluation.
Genetic Testing vs Genetic Screening
| Feature | Genetic Testing | Genetic Screening |
|---|---|---|
| Main purpose | Looks for specific genetic changes or variants. | Identifies people who may have increased risk. |
| Typical approach | Examines an individual's genetic material. | Can be applied to a population or defined group. |
| Result | May identify a genetic variant or help investigate a genetic condition. | Usually estimates whether risk is higher or lower. |
| Does it automatically diagnose disease? | Not always; interpretation depends on the test and clinical context. | No. Screening is generally not the same as diagnosis. |
| Next step after an abnormal result | Further clinical interpretation may be needed. | Additional evaluation or diagnostic testing may be considered. |
How Does Genetic Testing Work?
Genetic testing usually begins with collection of a biological sample. Depending on the test, the sample may come from blood, saliva, cells collected from the inside of the cheek, or another type of tissue.
The laboratory then analyzes the sample using a method appropriate for the genetic question being investigated.
Some tests examine a single gene, while others examine many genes or much larger portions of DNA.
The result is then interpreted in the context of the person's medical history, family history, and the purpose of the test.
How Does Genetic Screening Work?
Genetic screening is designed to identify people who may have a higher or lower likelihood of a particular genetic condition compared with an appropriate reference population.
Screening may be offered because a condition is sufficiently important to identify early, because a particular population has an increased risk, or because a screening program is designed to identify people who may benefit from further evaluation.
For example, newborn screening programs can identify infants who may have certain inherited or metabolic conditions. Other forms of screening may be used in reproductive, prenatal, or population-health settings.
Why a Positive Screening Result Is Not a Diagnosis
This is one of the most important differences to understand.
A screening test estimates risk. It does not necessarily establish that a genetic condition is present.
A person can receive a positive screening result without actually having the condition. This is called a false-positive result.
Similarly, a negative screening result can reduce the estimated risk but may not completely eliminate the possibility of a condition. This can occur because screening tests have limitations and cannot detect every possible genetic change.
When appropriate, healthcare professionals may recommend additional testing or evaluation after an abnormal screening result.
Types of Genetic Tests
1. Single-Gene Testing
Single-gene testing focuses on one gene. It may be useful when a person's symptoms or family history suggest a condition associated with a particular gene.
2. Genetic Panel Testing
A genetic panel examines multiple genes in one test. Panels may be useful when a condition can result from changes in several different genes.
3. Exome Sequencing
Exome sequencing examines the protein-coding regions of many genes. These regions are called exons and together make up the exome.
4. Whole-Genome Sequencing
Whole-genome sequencing examines a much larger portion of an individual's DNA than targeted testing. It can be useful in some complex cases when other testing has not identified an explanation.
5. Chromosomal Testing
Chromosomal tests look for larger changes involving chromosomes, such as changes in chromosome number or structure.
Genetic Screening and Genetic Testing in Healthcare
Genetic screening and testing can play different roles in healthcare.
Screening may help identify people who could benefit from further evaluation. Genetic testing may then be used to investigate a specific genetic question.
For example, if a screening process identifies an increased likelihood of a genetic condition, additional testing may sometimes be considered to determine whether a relevant genetic change is actually present.
The exact process varies according to the condition, the type of screening, the person's circumstances, and the healthcare system involved.
Genetic Counseling and Genetic Testing
Genetic information can sometimes have implications for other family members because relatives may share genetic variants.
Genetic counseling can help people understand why testing is being considered, what different results could mean, and what questions should be discussed with a healthcare professional.
According to the CDC, genetic counseling can help individuals and families make informed decisions about genetic testing and understand the meaning of results.
Benefits of Genetic Testing
- It can help investigate a suspected genetic condition.
- It may identify a genetic variant associated with a condition.
- It can provide information about inherited genetic risk in appropriate situations.
- It may provide useful information for family members.
- Some results can help healthcare professionals make informed medical decisions.
Limitations of Genetic Testing
Genetic testing is powerful, but it does not provide a complete picture of a person's health.
- Not every genetic variant is known or understood.
- Not every genetic condition can be detected by every test.
- A genetic variant may not always clearly predict whether a person will develop a condition.
- Results can sometimes be difficult to interpret.
- Genetic information may have implications for biological relatives.
For these reasons, genetic test results should be interpreted in the appropriate clinical context rather than viewed in isolation.
Genetic Testing vs Genetic Screening: Simple Example
Imagine a population contains 10,000 people.
A screening program may be designed to identify a smaller group of people whose risk appears higher than average.
After screening identifies someone as potentially higher risk, a more specific genetic test may be considered when appropriate to investigate whether a particular genetic change is present.
This simplified example shows the basic idea:
↓
Further evaluation/testing → investigates the genetic question
What About Direct-to-Consumer Genetic Tests?
Some genetic tests are marketed directly to consumers. These may provide information about ancestry, traits, or selected health-related genetic variants.
However, direct-to-consumer testing does not necessarily provide the same information or interpretation as clinical genetic testing.
Consumers should understand what a particular test can and cannot tell them before relying on its results. Health-related results may require confirmation or professional interpretation.
Frequently Asked Questions
Is genetic screening the same as genetic testing?
No. Genetic screening generally identifies people who may have an increased risk of a genetic condition, while genetic testing examines genetic material for specific changes or variants.
Does a positive genetic screening result mean I have a disease?
No. A positive screening result generally indicates increased risk and does not automatically establish a diagnosis.
Can genetic testing diagnose a genetic condition?
Some genetic tests can help confirm or rule out a suspected genetic condition, but the meaning of a result depends on the particular test and the individual's clinical context.
What samples are used for genetic testing?
Depending on the test, samples may include blood, saliva, cheek cells, or other tissues. The appropriate sample depends on the test being performed.
Is one genetic test able to detect every genetic disease?
No. Different genetic tests examine different genes, chromosomes, or portions of the genome. No single test detects every possible genetic condition.
Why is genetic counseling important?
Genetic counseling can help individuals understand why testing may be appropriate, what different results might mean, and how genetic information could affect them and their families.
Key Takeaways
- Genetic screening generally estimates risk and helps identify people who may need further evaluation.
- Genetic testing examines DNA, chromosomes, or related biological material for genetic changes.
- A positive screening result does not automatically mean a person has a genetic condition.
- Different genetic tests answer different biological questions.
- Genetic counseling can help people understand testing options and results.
- Genetic information should be interpreted in the appropriate medical and family-history context.
References and Further Reading
National Human Genome Research Institute (NHGRI): Genetic Screening and Genetic Testing.
Centers for Disease Control and Prevention (CDC): Genetic Testing and Genetic Counseling.
MedlinePlus Genetics: Genetic Testing and differences between screening and diagnostic testing.
Educational note: This article is intended for general biology and health education. It is not a substitute for medical advice, diagnosis, or individualized genetic counseling.
