Diagnostic testing occurs when an individual is showing signs or symptoms associated with a specific condition. Genetic testing can be used to arrive at a definitive diagnosis in order to provide better prognosis as well as medical management and/or treatment options. Testing can reveal conditions can be mild or asymptomatic with early treatment, as oppose to debilitating without treatment (such as phenylketonuria). Genetic tests are available for a number of genetic conditions, including but not limited to: Down syndrome, sickle cell disease, Tay–Sachs disease, muscular dystrophy. Establishing a genetic diagnosis can provide information to other at-risk individuals in the family.