Guthrie test is done in neonates for mass screening of

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