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KMID : 0918520160160020086
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Journal of the Korean Society of Inherited Metabolic Disease
2016 Volume.16 No. 2 p.86 ~ p.92
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A Study on Effectiveness of Conventional Phenylalanine Loading before BH4 Loading Test in Children with Hyperphenylalaninemia
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Park Young-Cheon
Kim Kang-In
Lee Jeong-Ho
Lee Dong-Hwan
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Abstract
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Purpose: The BH4 loading test is an important test that distinguishes PKU from BH4 deficiency and identifies the BH4 reactivity of PKU patients. Phenylalanine and BH4 loading tests are useful methods that can shorten the length of hospital stay while improving patients’ convenience. However, sufficient research on the dose of phenylalanine loading and BH4 administration time after the loading has not been carried out. The present study investigates the effectiveness of the existing phenylalanine loading method by analyzing the medical records of six patients who underwent the BH4 loading test after taking 100 mg/kg of phenylalanine patients.
Methods: The medical records of six patients who underwent the BH4 load test after taking 100 mg/kg of phenylalanine were examined out of 207 patients who were followed up in the Genetic Metabolic Clinic in Soonchunhyang University Hospital. All of the six patients had a low phenylalanine diet. First, they were taking 100 mg/kg of phenylalanine. 3 hours later, 20 mg/kg of BH4 were loaded. The phenylalanine levels in the blood were continuously measured at 1, 2, 4, 6, 8, 12, and 24 hours by setting the time the BH4 was loaded as the basal.
Results: The average of the highest phenylalanine concentrations of six patients was 20.0±11.70 mg/dL. One reached the highest concentration seven hours after taking phenylalanine; another reached it five hours after that, and the remaining three reached it four hours after that. Only one patient reached the highest concentration within three hours. The phenylalanine levels of four out of six patients (66%) rose above 400 μmol/L after being loaded with phenylalanine. The phenylalanine levels of the remaining two were 6.1 mg/dL (366 μmol/L) and 5 mg/dL (300 μmol/L), respectively.
Conclusion: One of six patients (16%) reached the highest concentration three hours after taking 100 mg/kg of phenylalanine and four patients (66%) reached 400 μmol/L or higher phenylalanine levels. There were patients whose phenylalanine levels did not rise above 400μmol/L using a commonly known test method; moreover, this method had the disadvantage of reaching the highest concentration after more than three hours. Therefore, it is considered that taking 200 mg/kg or more of phenylalanine and performing BH4 loading four to six hours after taking phenylalanine are helpful in proper diagnosis.
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KEYWORD
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Hyperphenylalaninemia, Tetrahydrobiopterin, Phenylalanine
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