Question
I have a 4-month-old baby, and after the doctor’s examination, it was found that he may have phenylketonuria. What kind of tests are needed for this disease?
Answer
For the diagnosis of phenylketonuria, a newborn screening is typically conducted. The Guthrie test is a common screening method, which detects the phenylalanine concentration in a dried blood spot on a culture plate. This test is usually performed within 2 to 3 days after the baby’s birth. The normal phenylalanine concentration in human serum is 1 to 3 mg/dL, while the concentration in phenylketonuria patients is usually twice or more than the normal value. In addition, urine purine tests can also be used for further diagnosis. These tests can help determine the type of phenylketonuria.