Question

Blood from which part of the body is tested for inborn errors of metabolism such as phenylketonuria?

1) Finger
2) Heel
3) Arm
4) Earlobe

Answer 1

Blood from the heel is tested for inborn errors of metabolism such as phenylketonuria, a condition caused by the inability to properly metabolize the amino acid phenylalanine (option 2).

Step-by-step explanation:

The test for inborn errors of metabolism such as phenylketonuria (PKU) is commonly performed on blood obtained from the heel of a newborn baby. PKU is a genetic disorder resulting from a deficiency in the enzyme phenylalanine hydroxylase, which is necessary for the conversion of the amino acid phenylalanine into tyrosine.

Without adequate enzyme activity, phenylalanine accumulates to toxic levels in the body, causing various health issues including neurological damage, hyperactivity, intellectual disability, and in severe cases, seizures and tremors. Blood from the heel is collected as it is a minimally invasive method to obtain a sufficient sample from a newborn for the PKU screening test, which is part of routine newborn screening programs in the United States and Canada.

Hence, the answer is option 2.