Several metabolic disorders which have early and severe manifestations may have their natural history significantly modified by the introduction of a treatment still on the pre-clinical phase. Pre-symptomatic diagnosis is only possible with the performance of screening tests in target populations, like newborns. The effort to perform a neonatal screening test should be done when a metabolic disorder fulfill the following criteria: 1) the disorders bring, if not treated, early and severe consequences to the health of the affected subject; 2) a treatment, which could substantially modify the natural history of the disease, is available; 3) the treatment is significantly more effective when introduced in the pre-clinical phase of the disease; 4) a laboratory test, which should be simple, efficient, low-cost and suitable for application in large scale, is available. With these conditions in mind, neonatal screening programs were initially introduced for phenylketonuria and congenital hypothyroidism, and presently are performed for the detection of a growing number of diseases. These programs are already well-established in developed countries, but their efficient application in developing countries is still a challenge.
Neonatal screening; Inborn errors of metabolism; Phenylketonuria; Congenital hypothyroidism
