DNA techniques for screening of inborn errors of metabolism.

Molecular genetic techniques are being used increasingly in newborn screening programs. Initial applications involved genotypic confirmation of positive screening tests by DNA microextraction or direct amplification from the dried blood spots. More recently we have shown that RNA can be microextracted from newborn screening specimens, treated with reverse transcriptase and amplified by the polymerase chain reaction. Primary DNA screening is being considered for medium chain acyl-CoA dehydrogenase deficiency in an attempt to identify and treat affected children before their first hypoglycemic episodes. An exciting new development is the application of DNA "fingerprinting" to the microorganisms used in the bacterial inhibition assays for quality control of these critical biological reagents. Thus, molecular genetic approaches will be valuable, not only for confirmatory testing, but also for primary newborn screening for inborn errors of metabolism.