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How are genetic conditions diagnosed?

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A doctor may suspect a diagnosis of a genetic condition on the basis of a person’s physical characteristics and family history, or on the results of a screening test.

Genetic testing is one of several tools that doctors use to diagnose genetic conditions. The approaches to making a genetic diagnosis include:

  • A physical examination: Certain physical characteristics, such as distinctive facial features, can suggest the diagnosis of a genetic disorder. A geneticist will do a thorough physical examination that may include measurements such as the distance around the head (head circumference), the distance between the eyes, and the length of the arms and legs. Depending on the situation, specialized examinations such as nervous system (neurological) or eye (ophthalmologic) exams may be performed. The doctor may also use imaging studies including x-rays, computerized tomography (CT) scans, or magnetic resonance imaging (MRI) to see structures inside the body.

  • Personal medical history: Information about an individual’s health, often going back to birth, can provide clues to a genetic diagnosis. A personal medical history includes past health issues, hospitalizations and surgeries, allergies, medications, and the results of any medical or genetic testing that has already been done.

  • Family medical history: Because genetic conditions often run in families, information about the health of family members can be a critical tool for diagnosing these disorders. A doctor or genetic counselor will ask about health conditions in an individual’s parents, siblings, children, and possibly more distant relatives. This information can give clues about the diagnosis and inheritance pattern of a genetic condition in a family.

  • Laboratory tests, including genetic testing: Molecular, chromosomal, and biochemical genetic testing are used to diagnose genetic disorders. Other laboratory tests that measure the levels of certain substances in blood and urine can also help suggest a diagnosis.

Genetic testing is currently available for many genetic conditions. However, some conditions do not have a genetic test; either the genetic cause of the condition is unknown or a test has not yet been developed. In these cases, a combination of the approaches listed above may be used to make a diagnosis. Even when genetic testing is available, the tools listed above are used to narrow down the possibilities (known as a differential diagnosis) and choose the most appropriate genetic tests to pursue.

A diagnosis of a genetic disorder can be made anytime during life, from before birth to old age, depending on when the features of the condition appear and the availability of testing. Sometimes, having a diagnosis can guide treatment and management decisions. A genetic diagnosis can also suggest whether other family members may be affected by or at risk of a specific disorder. Even when no treatment is available for a particular condition, having a diagnosis can help people know what to expect and may help them identify useful support and advocacy resources.

For more information about diagnosing genetic conditions:

Genetics Home Reference provides information about genetic testing and the importance of family medical history. Additionally, links to information about the diagnosis of specific genetic disorders are available in each condition summary under the heading “Where can I find information about diagnosis or management of...?”

Genetic Alliance provides an in-depth guide about genetic counseling called Making Sense of Your GenesP D F fileThis link leads to a site outside Genetics Home Reference., which includes information about how genetics professionals diagnose many types of genetic disorders.

This article from Nature EducationThis link leads to a site outside Genetics Home Reference. discusses the diagnosis of several well-known genetic conditions.

The Centers for Disease Control and Prevention (CDC) offers a fact sheet about the diagnosis of birth defectsThis link leads to a site outside Genetics Home Reference., including information about screening and diagnostic tests.

Boston Children’s Hospital provides this brief overview of testing for genetic disordersThis link leads to a site outside Genetics Home Reference..

The American College of Medical Genetics offers practice guidelinesThis link leads to a site outside Genetics Home Reference., including diagnostic criteria, for several genetic disorders. These guidelines are designed for geneticists and other healthcare providers.

The Agency for Healthcare Research and Quality’s (AHRQ) National Guideline Clearinghouse has compiled screening, diagnosis, treatment, and management guidelinesThis link leads to a site outside Genetics Home Reference. for many genetic disorders.

GeneReviewsThis link leads to a site outside Genetics Home Reference., a resource from the University of Washington and the National Center for Biotechnology Information (NCBI), provides detailed information about the diagnosis of specific genetic disorders as part of each peer-reviewed disease description.

Next: How are genetic conditions treated or managed?

Published: February 11, 2013