Principle of ELISA :
Enzyme linked Immunosorbent Assay (ELISA) is based on the interaction between antigen and antibody.
Phenylketonuria :
Phenylketonuria is an autosomal recessive disorder. Phenylalanine hydroxylase enzyme is non-functional in this disorder due to which tyrosine is converted into phenylpyruvate and ketone bodies. These byproducts are excreted in the urine.
ELISA for phenylketonuria :
To perform ELISA, either antibody should be produced by the host immune system or antigen should be present. In phenylketonuria, both antibodies and antigens are not produced because it is a genetic disorder. Therefore, ELISA cannot be used for the diagnosis of phenylketonuria.