  Genetic testing carried out at the population level—for any of these purposes—is referred to as genetic screening. Newborn screening programs to diagnose conditions like PKU, hemoglobinopathies, etc. on the basis of blood components and circulating metabolites have been carried out for several decades in many jurisdictions; while such screening could be expanded to include genetic tests for many more diseases, without effective treatment measures, this is of limited use. Ethical debate exists over whether newborn screening should be mandatory (see Andrews 1994). While successful population-based carrier screening has been carried out in Sardinia for beta-thalassemia and for Tay-Sachs among U.S. Ashkenazi Jews, the negative impacts of testing for sickle-cell anemia among African Americans provide caution for launching further such programs—outcome is likely to depend on the social status of the targeted group (Duster 1990). The pathway from gene discovery to population-level screening is not straightforward, however. Although the gene implicated in CF was identified in 1989, statements issued by the American Society of Human Genetics in 1990 and 1992 and by a NIH workshop in 1990 recommended against instituting population-based carrier screening because adequate detection rates were compromised by the heterogeneity of mutations found; in addition, the clinical course of the disease remained difficult to predict, and resources for education and counseling were lacking (ASHG 1990; ASHG 1992; NIH Workshop  1990).[45]