Testing environment for single-gene disorders in U.S. reference laboratories.

Molecular diagnosis is the detection of pathogenic mutations in DNA and RNA samples prepared from at-risk patients. Principles underlying DNA-based diagnosis originate from localization and identification of genes responsible for human disease and the characterization of pathogenic mutations; new diagnostic tests are in constant development. Indications for testing include diagnosis, carrier risk revision, prenatal diagnosis, presymptomatic diagnosis, and population screening. The majority of DNA diagnoses are performed in a reference laboratory in which the referring physician, rather that the patient, is the client of the laboratory. Thus, the role of the genetic counselor in a reference laboratory is quite different from traditional clinical practice. As with all clinical laboratory tests, molecular diagnostics are interpreted within the context of the patient's overall clinical presentation and are overlaid with regulatory programs of quality assurance, quality improvement, and quality control. The greatest challenges facing the clinical laboratory are genetic heterogeneity, cost control, regulatory and patent compliance, technology transfer, and the genetic education of the referring physician.