Cascade testing in hereditary genetics is best described as testing which group?

• A. The index patient only
• B. Unrelated individuals only
• C. Relatives of the index patient for a known familial variant, to inform risk and management
• D. Only preconception couples

Answer: (C)

Cascade testing is the process of testing relatives of an affected individual for a known familial pathogenic variant to determine who is at risk and to guide clinical management. Once the index patient is found to carry a familial variant, targeted testing is offered to relatives who may share the same variant, enabling tailored surveillance, preventive steps, and informed decisions about future health and reproduction. This approach relies on having a known variant to test for within the family, and it is not limited to testing the index case alone, nor to unrelated individuals, and it isn’t restricted to preconception couples.