Urine screening for metabolic disease in newborn infants.

A new method for urine screening for metabolic disease in newborn infants is described. A battery of bacterial inhibition assays to test urine-impregnated filter paper from 3- to 4-week-old infants for amino acids, purines, and pyrimidines was used. We were able to establish the accuracy and efficiency of the method by examining 289 unknown specimens from other laboratories and by collecting and testing 18,400 newborn infants' urine specimens. The major advantages over existing chromatography methods are that: (1) the technology to perform the test already exists in most laboratories screening for metabolic disorders; (2) it is relatively inexpensive; (3) collection of the sample is easy and cooperation of the parents is good; (4) the false positive rate is low (0.9%); and (5) tests can be targeted to detect clinically significant disorders. In this screening program, we detected two cases of persistent neonatal tyrosinemia, two cases of cystinuria, and one case of citrullinemia. These results suggest that urine screening is a good adjunct to blood screening of newborn infants.