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Serum phenylalanine screening   

Overview | Risks | Results

Alternative names:

Phenylalanine; Phenylalanine - serum

Definition:

The serum phenylalanine screening is a test that screens for the disease Phenylketonuria (PKU) by detecting elevated levels of phenylalanine.

How the Test is Performed

Infant:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. Three drops of blood are placed in three separate test circles on a piece of paper. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

The test paper is taken to the laboratory where it is mixed with a type of bacteria that needs phenylalanine to grow, and another substance that inhibits phenylalanine from reacting with anything else.

How to Prepare for the Test

Infants and children:
For the physical and psychological preparation you can provide for your child, see the following topic:

• Infant test or procedure preparation (birth to 1 year)

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the Test is Performed

This test is performed on infants to screen for phenylketonuria PKU. This disease is caused by a deficiency of the enzyme needed to breakdown the amino acid phenylalanine.

If PKU is not detected early, an affected infant will beome mentally retarded as the amino acid level builds up. However, if it is detected early, the severe side effects of PKU may be avoided through diet modification. Therefore, even though the condition is relatively rare, most newborns are screened.

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