Phenylketonuria (PKU) Screening

Phenylketonuria (PKU) screening is an important check for newborn screening. Phenylketonurics (PKU) is a common amino acid metabolic disease caused by an enzyme deficiency in the phenylalanine metabolic pathway, which prevents phenylalanine from being converted into tyrosine, resulting in phenylalanine and its Ketoacid accumulates and is excreted in large quantities from the urine. The main clinical manifestations are mental retardation, seizures and hypopigmentation. The disease is autosomal recessive. Phenylalanine is one of the essential amino acids in the body. The daily intake of normal people is about 200-500 mg, of which 1/3 is for synthetic protein, and 2/3 is converted to tyrosine by phenylalanine hydroxylase (PAH) in hepatocytes. Synthetic thyroxine, adrenaline and melanin. In the process of converting phenylalanine to tyrosine, in addition to PAH, tetrahydrobiopterin (BH4) must be involved as a coenzyme. Basic Information Specialist classification: growth and development examination classification: blood examination Applicable gender: whether men and women apply fasting: fasting Tips: Choose plant or animal protein with high nutritional value, such as milk, eggs, fish, lean meat, various soy products. Normal value The phenylalanine content is 0.06 - 0.18 mmol / L (1 - 3 mg / dl). Clinical significance Abnormal results: 1, the nervous system Early neurological behavior abnormalities, such as excitement, hyperactivity or lethargy, wilting, a few showed increased muscle tone, hyperreflexia, convulsions (about 25%), followed by intelligent development, 80% have EEG abnormal. BH4-deficient neurological symptoms appear earlier and more severe, common muscle tone is reduced, lethargy, convulsions, such as non-treatment, often died in early childhood. 2, appearance Due to insufficient synthesis of melanin, the hair, skin and iris are lighter in color months after birth. Dry skin, and sometimes accompanied by eczema. 3, other Due to the discharge of phenylacetic acid in urine and sweat, it has a special rat urine odor. People who need to check: Parents have this symptom and their newborns have the above symptoms. High results may be diseases: phenylketonuria, phenylketonuria in children Taboo before the examination: poor rest, improper diet, excessive fatigue. Requirements for inspection: Actively cooperate with the doctor's work. Inspection process After 3 days of feeding, the roots of the feet were collected, absorbed on the thick filter paper, dried and mailed to the screening center. The Guthrie bacterial growth inhibition test was semi-quantitatively determined. The principle is that phenylalanine can promote the inhibition. Bacillus subtilis re-growth, the content of benzene tyrosine in blood was determined by the range of growth circle, and the colorimetric quantitative determination was also carried out under the action of phenylalanine dehydrogenase, and the false positive rate was low. When the phenylalanine content is >0.24mmol/L (4mg/dl), which is twice the normal reference value, venous blood should be reviewed or quantified for phenylalanine and tyrosine. Normal human phenylalanine concentration is higher in children with plasma phenylalanine up to 1.2mmol/L (20mg/dl), and the blood tyrosine is normal or slightly lower. Not suitable for the crowd 1. Patients who have taken contraceptives, thyroid hormones, steroid hormones, etc., may affect the results of the examination and prohibit patients who have recently taken the drug history. 2, special diseases: patients with hematopoietic function to reduce disease, such as leukemia, various anemia, myelodysplastic syndrome, etc., unless the examination is essential, try to draw less blood. Adverse reactions and risks 1, subcutaneous hemorrhage: due to pressing time less than 5 minutes or blood draw technology is not enough, etc. can cause subcutaneous bleeding. 2, discomfort: the puncture site may appear pain, swelling, tenderness, subcutaneous ecchymosis visible to the naked eye. 3, dizzy or fainting: in the blood draw, due to emotional overstress, fear, reflex caused by vagus nerve excitement, blood pressure decreased, etc. caused by insufficient blood supply to the brain caused by fainting or dizziness. 4. Risk of infection: If you use an unclean needle, you may be at risk of infection.

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