Patient's question:
Baby was born not long ago, and her urine is a bit yellow, I'm afraid it might be something like an upset stomach, so I took her to the hospital for a thorough examination. However, during the detailed examination, it was found that it might be phenylketonuria. Phenylketonuria is positive, but the doctor said that a re-examination needs to be carried out. If the diagnosis is confirmed, it will be necessary to go to the hospital for treatment. ?How many phenylketonuria tests are positive?Doctor's answer:
Phenylketonuria (PKU) is a genetic disorder caused by a deficiency in enzymes of the phenylalanine metabolic pathway, which prevents phenylalanine from being converted into tyrosine. This leads to the accumulation of phenylalanine and its ketone bodies, resulting in their excretion in large amounts in the urine. In normal individuals, blood phenylalanine levels range from 60 to 180 μmol/L, while in PKU patients, it can be as high as 600 to 3600 μmol/L. If 258 μmol/L is used as the cutoff point to distinguish between normal individuals and PKU patients, there can be as high as 4% false positives. Chromatographic methods can lead to false negatives in newborns within the first few days of life. MS/MS methods can increase the rate of false positives.