Costs and benefits of prenatal screening for cystic fibrosis.

New tests promise to facilitate the prenatal detection of cystic fibrosis (CF), a fatal genetic disorder. This study examines the costs and benefits of prenatal screening and selective abortion using two types of tests: those based on restriction fragment-length polymorphisms (RFLPs), which can only be applied when genetic material is available from a CF-affected family member; and those based on probes for the newly discovered CF gene, which can be applied in the general population. When either type is applied in families of CF-affected children, even an expensive test produces substantial net benefits. Existing direct gene probe tests are not sensitive, although eventually they may become less expensive and more accurate than tests based on RFLPs. Even if these tests become highly accurate, the financial benefits of population-wide screening for CF are likely to be small or negative, particularly if testing does not lead to increases in the number of normal children as it decreases the number of births of CF-affected children. Because few children born in families without a history of CF have the disease, tests that are not perfectly specific will produce a large number of false-positive results, leading to the abortion of many normal fetuses.