6 screening methods for the amino acid metabolic disease phenylketonuria

(1) Neonatal screeningAfter 3 days of feeding, blood is collected from the amino acid disorder ends of the feet and then collected on thick recycled filter pape...

Apr 01,2022 | Janet

(1) Neonatal screening

After 3 days of feeding, blood is collected from the amino acid disorder ends of the feet and then collected on thick recycled filter paper that is dried at the local hospital and mailed to the screening center.

The screening center uses the guthrie bacterial growth inhibition test for semi-quantitative determination.

The principle is to use l-phenylalanine to stimulate the growth of an already inhibited Bacillus subtilis. The accuracy of disease detection is high and the probability of false positive is low.

(2) Urine iron trichloride test

Screening of older infants and children. The test uses the reaction of a ferric chloride solution with phenylalanine in the urine.

If there is an immediate green reaction, the urine is positive for a high concentration of phenylalanine.

The dinitrophenylhydrazine test can also be used to detect phenylalanine in urine. The principle is similar to that of the ferric chloride test, and a yellow precipitate is positive.

(3) Analysis of plasma amino acids and analysis of urine organic acids

This test can detect not only this condition, but also other amino acid deficiency conditions and related metabolic diseases

(4) Urine pterin analysis

To determine abnormal pterin levels in the body by analyzing urinary levels of neopterin and biopterin using high pressure liquid chromatography (PHLC).

(5) Enzymatic diagnosis

Pah is present only in liver cells and requires liver biopsy to detect the enzyme activity, which is not suitable for clinical diagnosis but usually only for academic research.

The activity of the other 3 enzymes can also be determined by extracting red, white or skin fibroblasts from peripheral blood.

(6) DNA analysis

Prenatal diagnosis is performed directly by DNA analysis in pregnant women who have the disease gene but no symptoms.