This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Maternal and child care, Subject name: Social & Preventive Medicine
Guthrie test is done in neonates for mass screening of 
Select and explain. 
A. Neonatal hypothyroidism, B. Hemoglobinopathies, C. Phenylketonuria, D. CDH
C: Phenylketonuria
Answer: C: Phenylketonuria 
Explanation: Phenylketonuria is a disorder of amino acid metabolism. This is an autosomal recessive trait in babies who are homozygous with a deficiency in the enzyme phenylalanine hydrolase which normally conves phenylalanine to tyrosine. Mass screening of blood phenylalanine in neonates is performed by the Guthrie test. Ref: Park; 23rd ed; Pg 535