<prompt> Phenylketonuria is detected by which urine test:Guthrie testSodium nitroprusside testBlot testFeCl3  <response>: Guthrie Test: It is a rapid screening test. Ceain strains of bacillus subtilis need phenylalanine as an essential growth factor. Bacteria cannot grow in a medium devoid of phenylalanine. Bacterial growth is propoional to the phenylalanine content in the patients blood. Good to know: Ferric chloride Test: Phenyl ketones in urine can be detected by this test. A transient blue-green color is a positive test. Nitroprusside Test is used for the colour reaction of amino acid Sulfhydryl group Cysteine. Ref: Textbook of Biochemistry DM Vasudevan, 5th Ed Page 22, 206 