Current approaches to genetic metabolic screening in newborns.

Genetic metabolic screening in newborn infants includes both specific testing for clinical indications in sick neonates and routine newborn screening. The decision of which sick neonates should have metabolic testing is based on the clinical phenotype and the results of general laboratory analyses, with particular attention to hypoglycemia, metabolic acidosis, and hyperammonemia. Metabolic tests include analyses for amino acids and organic acids and a carnitine profile. Routine newborn screening should be performed on all neonates prior to hospital discharge but no later than the 3rd day of life. The disorders covered by newborn screening vary among the states and among countries but virtually always include phenylketonuria and congenital hypothyroidism and often include sickle cell disease and galactosemia. Other metabolic disorders that may be included in newborn screening are maple syrup urine disease, homocystinuria, biotinidase deficiency, and congenital adrenal hyperplasia.