Question

How many cases of Phenylketonuria are positive?

Answer

Phenylketonuria is a genetic disorder caused by an enzyme defect in the metabolism of phenylalanine, leading to the inability to convert phenylalanine into tyrosine, which results in the accumulation of phenylalanine and its ketones in the body and their excessive excretion in urine. Normal blood phenylalanine levels are approximately 60 to 180 μmol/L, whereas in patients with phenylketonuria, the levels can reach 600 to 3600 μmol/L. If 258 μmol/L is used as the threshold between normal and phenylketonuria patients, there can be as high as a 4% false-positive rate. False-negative results may occur within a few days after a newborn’s birth when using chromatography. The false-positive rate can be improved with MS/MS detection.