This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: NEET 2018, Subject name: Biochemistry
True regarding PKU is all except:- 
Select and explain. 
A. Due to deficiency of phenyl alanine hydroxylase, B. Neurological symptoms are due to excess phenyl alanine, C. Blood phenyl alanine level >20 mg/dl causes severe disease, D. Method of choice for screening is urinary phenyl alanine by Guthrie;s test
D: Method of choice for screening is urinary phenyl alanine by Guthrie;s test
Answer: D: Method of choice for screening is urinary phenyl alanine by Guthrie;s test 
Explanation: Diagnosis of PKU was detected by screening the new-born babies for the increased plasma levels of phenylalanine (PKU, 20-65 mg/dl; normal 1-2mg/dl). This was carried out by Guthrie test, which is a bacterial (Bacillus subtilis) bioassay for phenylalanine. Phenylpyruvate in urine can be detected by ferric chloride test (a green colour is obtained). Method of Choice is Tandem Mass Spectrometry, also for all the Inborn metabolic Error disease