Genetic Tests Find Mutations, NOT Disease
An accurate gene test can tell if a mutation is present, but that finding does not guarantee that disease will develop.
For example, women with the BRCA1 breast cancer susceptibility gene have an 80 percent chance of developing breast cancer by the age of 65. The risk is high but not absolute. And family members who test negative for the BRCA1 mutation are not exempt from breast cancer risk; over time, they can acquire breast cancer-associated genetic changes at the same rate as the general population.