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Understanding genetic testing
Audience: patients-public, students-learners ยท Review state: published
What it is
Genetic testing examines your DNA, the instruction set in every cell, for changes that cause or raise the risk of disease. A sample of blood, saliva, or cheek cells is analyzed in a laboratory.
It is used to diagnose genetic conditions, find out whether you carry a variant you could pass to children, estimate risk of certain diseases such as some cancers, and guide which medicines will work best for you.
Common uses
Diagnostic testing confirms a suspected condition such as cystic fibrosis. Carrier screening tells prospective parents whether they carry variants for inherited conditions. Prenatal and newborn testing look for conditions before or just after birth.
Predictive testing estimates future risk, for example BRCA gene testing for breast and ovarian cancer risk. Pharmacogenetic testing matches medicines to your genetic makeup, avoiding drugs that would work poorly or cause side effects for you.
What results mean
Results are not simple yes-or-no answers. A positive result for a risk variant means higher chance, not certainty, and a negative result does not guarantee protection. Some results are variants of uncertain significance - changes science cannot yet interpret.
Results can also have implications for blood relatives, who may share the variant, which is part of why testing decisions deserve thought.
Deciding whether to test
Medical genetic testing is ordered for a reason: a strong family history, a suggestive pattern of disease, or a treatment decision it would change. Genetic counseling before and after testing helps you understand what the test can and cannot tell you, and what you would do with each possible result.
Direct-to-consumer tests offer ancestry and some health information, but their health results are limited in scope and accuracy, and unexpected findings need confirmation and interpretation by clinical services.
Limitations
General educational overview, not medical advice. Test selection and result interpretation belong with clinical genetics services and counselors.