PROCEDURE: NEWBORN METABOLIC SCREENING FOR PKU

OBJECTIVE: Early detection of phenylketonuria

INDICATIONS: All newborns

WHEN PERFORMED: Around day 2

SPECIMEN(S) NEEDED: Blood obtained from a heel-stick applied to filter paper and dried

METHOD: Blood spots are punched out of filter paper and applied to gels that contain bacteria. Each gel is incubated under conditions that would prompt bacterial growth only if there were an excess of phenylalanine in the blood sample. A few laboratories use a fluorometric method for detection of phenylalanine.

ANALYSIS: Each gel is examined for bacterial growth. The presence of bacteria around a blood spot indicates the presence of an excess amount of phenylalanine in the blood spot.

OTHER: Once the identification has been made, follow-up confirmatory blood testing is performed. When a diagnosis has been confirmed, therapy (dietary or drug) can be immediately started. Failure to start therapy early can result in long term developmental disabilities. Newborn screening is an inexpensive process (generally under $5.00 per condition tested) mandated by many state legislatures.

Prior to the initiation of newborn screening in the early 1960s, infants born with recessive metabolic disorders were likely to be severely mentally retarded and ultimately institutionalized. The success of screening programs has reduced the immediate effect of recessive metabolic diseases, but increases the prevalence of the PKU gene in the gene pool since all affected fertile individuals must pass a PKU gene on to each child.