Prevention or amelioration of disease is possible if risk or susceptibility factors can be identified and effective interventions are available. For example, phenotype testing of neonates for rare disorders such as phenylketonuria, other heritable amino acid metabolism defects, galactosemia, and congenital hypothyroidism is universal or mandatory because timely diagnosis and management avert disease manifestations. In diverse, typically adult-onset disorders, it is feasible to detect pathogenic germline or acquired mutations in individuals, family members, or population cohorts. Some clinicians rely on DNA analyses to assess the risk of single-mutation disorders such as familial breast and colon cancer, hemochromatosis, and Huntington disease. Among these examples, the risk of symptoms is great in Huntington disease, but the potential to prevent symptoms and consequent death is low. In HFE hemochromatosis, the capability to prevent disease due to iron overload is great, but the risk that subjects with a “positive” genetic test will develop severe iron overload is relatively low. Many physicians and non-medical members of the public have difficulty understanding the indications for, and interpreting results and consequences of, genetic information for risk assessment or diagnosis.

Across certain disorders, some studies and many anecdotes suggest that the potential for misuse and misunderstanding is greater for DNA-based tests than for phenotype tests, even one like hemoglobin electrophoresis that has diagnostic and predictive value equivalent to that of corresponding DNA-based testing. In the 1990s, controversy about the privacy, confidentiality, and fairness of use of genetic information increased.