phe stands for Phenylalanine, which means phenylalanine, and is one of the 20 common amino acids. Phenylalanine is an essential amino acid for the body and is consumed by people through their diet. Phe is an indicator to screen for phenylketonuria. Phenylketonuria (PkU) is a common disorder of amino acid metabolism, mainly due to the lack or reduced activity of phenylalanine hydroxylase or the enzyme related to the synthesis of coenzyme tetrahydrobiopterin, which prevents tissues in the body from converting phenylalanine to tyrosine, resulting in the accumulation of phenylalanine and its metabolites in the body, causing a series of functional abnormalities and the excretion in the urine of affected children of Phenylalanine and its metabolites accumulate in the body, causing a series of functional abnormalities. Clinical features include mental retardation, seizures, and hypopigmentation. Phenylketonuria causes severe pain and trauma to the child and family. In atypical phenylketonuria, if the sequelae are detected too late, the disease becomes more severe, with severe mental retardation and also intractable epilepsy. Therefore, it is important to detect and treat children with phenylketonuria as early as possible, with newborn screening being the most effective method of early detection of the disease. The specific practice of screening for phenylketonuria in our country is that newborns are nursed for 3 to 7 days, peripheral blood is collected by needle pricking the heel and dripping on a special filter paper for blood collection, after drying, it can be sent to the screening laboratory for determination of phe concentration, if the phe concentration is less than the cut-off value, it is phe negative, and the negative result indicates that the child has normal phenylalanine in the blood; if the phe concentration is greater than the cut-off value, it is phe A positive result indicates that the blood phenylalanine concentration is higher than normal and that hyperphenylalaninemia may exist, requiring further venous blood testing to confirm the diagnosis. Phenylalanine concentration measurement: normal phenylalanine concentration <120umol/L (2mg/dl), classic phenylketonuria blood phenylalanine concentration >1200umol/L, moderate phenylketonuria blood phenylalanine concentration >360umol/L to <1200umol/L, mild phenylketonuria blood phenylalanine concentration >120umol/L to ≤ 360umol/L.