Question

A mother brings her 3 week old infant to a clinic for a phenylketonuria re-screening blood test. The test indicates a serum phenylalanine level of 1 mg/dl (60.5 mcmol/L). The nurse reviews this result and makes which interpretation?

1. It is positive
2. It is negative
3. It is inconclusive
4. It requires screening at 6 weeks

Answer 1

A serum phenylalanine level of 1 mg/dl (60.5 mcmol/L) indicates a negative result for phenylketonuria (PKU) in a 3-week old infant, meaning that the infant does not have elevated levels of phenylalanine suggesting the absence of PKU.

Step-by-step explanation:

The result of a phenylketonuria re-screening showing a serum phenylalanine level of 1 mg/dl (60.5 mcmol/L) for a 3-week old infant is negative. Phenylketonuria (PKU) is an autosomal recessive inherited disorder where there is a deficiency in the enzyme phenylalanine hydroxylase, necessary for converting phenylalanine to tyrosine. A high level of phenylalanine is toxic and can cause neurological damage and developmental issues. Therefore, this test result, which falls within the normal range, indicates that the infant does not show elevated levels of phenylalanine and hence is likely not affected by PKU. It's essential for infants diagnosed with PKU to adhere to a strict low-phenylalanine diet to prevent brain damage and other severe symptoms. In this scenario, no additional screening is necessary at 6 weeks based on this result alone.