Such tests were first introduced to investigate some genetic diseases that occur in adulthood or old age. Among these diseases were Huntington's disease, ALS and Alzheimer's disease; But now this possibility has been provided for many diseases.
Most of the diseases that can be diagnosed before symptoms appear, are transmitted in the autosomal dominant way as you can see in the picture below, and therefore, people at risk are exposed to 50% of the disease before symptoms appear. Genetic examination of such people will change them from "at risk" to "free from risk" or vice versa to "waiting for symptoms" (unknown time of occurrence).
Although this category of reviews solves many issues for people at risk and can be comforting; But it will also raise new issues.
Due to the importance of the issue, people at risk should be given counseling before and after the test, and various situations should be explained to them in detail before taking any action.