the vast majority of results will be in the normal range, a tendency that reduces the vigilance of those performing the test;
the nature of genetic disorders increases the chance of errors in interpretation;
tests at the DNA level may not detect all disease-causing or susceptibility-conferring mutations, resulting in false negative results; and
a positive test result cannot always predict disease severity and, in some instances, may falsely predict the future occurrence of disease particularly in tests for predispositions to multifactorial disorders and disorders of variable expressivity.
This chapter reviews current programs and regulations for assessing the quality of laboratories providing genetic tests, including the interpretation of test results, and current provisions for assessing the safety and effectiveness of genetic test kits and their critical components. For purposes of the committee's definition, genetic tests are those that are used primarily for predicting the risk of genetic or gene-influenced disease either in the person being tested or in his or her descendants. Tests that are used primarily for other purposes, but may contribute to diagnosing a genetic disease (e.g., blood smears, certain serum chemistries), would not be covered by this definition.
Because the field of genetic testing is developing very rapidly, few systematic data are available on how many genetic tests are being done, who is doing them, or how well they are being done (Meaney, 1992). Some data are available on newborn screening (Holtzman et al., 1986; Hannon and Adam, 1991; Adam and Hannon, 1992; CORN, 1992). Similarly, few published data on genetic laboratory quality are available (Holtzman et al., 1986; Hommes et al., 1990; Hannon and Adam, 1991; Meaney, 1992). To assess the nature and extent of special laboratory issues in human genetics, therefore, the committee held an expert workshop to review existing voluntary, professional, and governmental regulatory efforts to ensure the quality of genetic laboratory testing (participants are listed in Appendix A of this report). Committee members also met with representatives of the Food and Drug Administration (FDA), the Health Care Financing Administration (HCFA), and the Centers for Disease Control and Prevention (CDC) to learn the agencies' current policies and plans for assessing the safety and effectiveness of genetic tests.
Identifying problems of the quality of genetic tests is complicated because of the ways in which they are provided. A few are sold as kits, primarily to clinical laboratories; these have to undergo scrutiny by the FDA. An increasing number of tests are being marketed as laboratory services by commercial laboratories and a few academic laboratories. Many more are being provided for clinical decisionmaking purposes by research laboratories in academic medical centers. Although the critical reagents (which usually are not part of FDA-approved kits) used for testing in commercial and research laboratories, and the laboratories themselves,